PHILADELPHIA — When he first got the call to the majors last month, the Arizona Diamondbacks’ Alek Thomas remembers pitchers attacking him in a standard fashion. Opposing teams went after him with fastballs away. They kept him honest with change-ups. He also saw the occasional breaking ball or cutter.

Sometime around his 10th game, he said, he began to notice a change. The fastballs away were replaced by fastballs inside. The change-ups were replaced by sliders, most of them inside under his hands. Teams had seen Thomas do damage on pitches over the plate, driving them to the opposite field. They had found a hole inside. They looked to exploit it. And for the past few weeks, Thomas has struggled to adapt.

“I’m trying to make that adjustment,” he said. “It’s a work in progress.”

Thomas’ experience is not unlike those of most hitters getting their first taste of the major leagues. The transition from Triple-A to the big leagues is considered the biggest jump a player has to make. Some believe the jump has never been bigger.

Several of baseball’s best prospects opened this year in the majors. Nearly all of them struggled — some of them badly — for several weeks. Many of them continue to struggle as the season enters its third month.

Pick an established star in the majors and odds are he endured growing pains early in his career. It does not happen to all hitters, but it happened to Mike Trout and Vladimir Guerrero Jr., Francisco Lindor and Mookie Betts, Josh Donaldson and J.D. Martinez. Some needed only weeks to adjust. Others needed multiple years. It is a phenomenon that predates baseball’s analytics era. It has only been amplified by it.

The Diamondbacks are one of several teams with a crop of young position players who are getting close to or have already reached the majors. Finding ways to ease their transition is a focus for some in the organization. But, there is also a belief that the struggles are a grim reality, and that only so much can be done to prepare young hitters.

“I think we do the best we can,” said Mike Elias, general manager of the Baltimore Orioles, another organization going through a youth movement. But he admits, “We think learning to be a hitter in the big leagues requires hitting in the big leagues at some point.”

There are two reasons most often cited to help explain why the jump is so difficult: talent and information. The two go hand-in-hand.

The talent is the most obvious.

In the minors, the best players at each level end up getting promoted. There is no level above the major leagues. Major league pitchers tend to not only have good arms that generate big fastballs and swing-and-miss secondary stuff, but they also have the ability to wed their stuff with command — and are able to do so more often than not rather than only occasionally.

Diamondbacks hitting coach Joe Mather notes that while the differences in ability from Triple-A to the majors aren’t enormous, they are evident across the board — and, taken together, they can be devastating for a young hitter.

“They hit their spots far more than they do in the minor leagues,” Mather said. “Their arms are generally good. There’s no day off. The fifth starter is still a big league starter and pretty good. Even though it’s a little bit more run or a little bit more cut or it’s on the black vs. just in off, it makes a big difference. The differences are so small, but they’re big.”

But the biggest factor might be the information. Major league clubs have staffs dedicated to producing scouting reports for their pitchers to follow, and they are able to identify hitters’ weaknesses and generate plans of attack better than anything hitters have seen in the minors. Combine that information with the talent to execute and hitters are often overwhelmed.

Diamondbacks third baseman Josh Rojas said that once players get to Triple-A they think they are merely one step away from being big leaguers. They are right in a sense, but they underestimate just how far they have to go, he said.

“It’s a giant step from Triple-A to the big leagues when it comes to facing the pitching,” Rojas said, emphasizing the word "giant." “I think everybody is kind of aware of what they hit well and what they don’t hit well, but it’s when you get here and they start to not only expose your holes but use your (strengths) against you with other pitches.”

When Rojas first reached the majors, he struggled with pitches on the outer half of the plate. He knew this, and he recognized that other teams were attacking him there. What caught him by surprise was the way they attacked him inside.

“When they would come in, it was either off the plate or it was something that looked like it was going to be good to hit and then it was out of the strike zone,” Rojas said. “They don’t just use what you don’t hit well, they’re going to make stuff look like what you do hit well, and then run it out of the zone. There’s a whole other adjustment period.”

Other factors exist, as well. The stage is larger, the pressure more intense, and the mental side of the game can be difficult to overcome, particularly for players who are failing for the first time in their careers. Many cannot keep themselves from worrying about their status and the potential for getting sent down, concerns that can often exacerbate their struggles.

So it is little surprise to see what has happened to many of the games prominent prospects this season. Kansas City Royals infielder Bobby Witt Jr. was hitting .220 after his first 100 at-bats. Seattle Mariners outfielder Julio Rodriguez ended April with a .205 average. Both have improved their numbers, Witt more modestly than Rodriguez, as the season has progressed.

The same is not true for Mariners outfielder Jarred Kelenic, who was sent back to the minors after starting the season 12 for 86 (.140), or Detroit Tigers first baseman Spencer Torkelson, who entered Friday with a .190 average through 51 games. Orioles catcher Adley Rutschman, widely regarded as the majors’ best prospect, made his debut three weeks ago. He is 8 for 56 (.143) in 15 games.

Mariners General Manager Jerry Dipoto doesn’t think it is a coincidence that so many of the game’s top prospects are struggling to the point “where they need a life preserver.” He thinks the loss of the 2020 minor league season due to the pandemic — plus the late start in the minors in 2021 — helps explains the extreme nature of their struggles.

“You’re coming into a league with 600 fewer plate appearance of experience than you should have had coming through the minors, and for all these guys it’s 600 plate appearances that they were robbed of at the mid- to upper-levels,” Dipoto said. “That’s when you’re accelerating your development and you’re ready to break through to the big leagues.

“There’s more velocity, there’s more spin; it’s never been as dramatic as it is. Then add on to that the fact that in 2022 they come into what has been one of the more muted offense-producing environments, really, in 40 years. It’s been a combination of events that really does help explain why so many of the best young players in the game have struggled.”

Like all teams, the Diamondbacks do their best to prepare hitters in the minors. Mather said players in the Diamondbacks’ minor league system are given updates every couple of weeks on what their strengths and weaknesses appear to be based on pitch data, giving them a chance to start trying to close their holes. Each of the organization’s minor league affiliates are outfitted with pitching machines — units that cost around $15,000 — that can spit out all types of pitches, creating more of a realistic practice environment.

“Getting them comfortable being uncomfortable there so hopefully they come up here and it clicks a little bit faster,” Mather said. “Hopefully, it doesn’t take a full season. Hopefully it takes half or three-quarters of a season. But you can’t completely bypass that hurdle that they have to get over.”

There are development challenges. A hitter at the Double-A level might face a pitcher with big-league caliber command once a week, Diamondbacks General Manager Mike Hazen said. The rest of the time he can usually wait out a pitcher for a mistake.

“Another team may know (Diamondbacks prospect) Corbin Carroll has a hole, but they may have two guys on their roster who can hit the hole,” Hazen said. “I’m not sure we’re doing ourselves a service to coach him and say, ‘Hey, look for this and work on this particular pitch. All these other pitches that you’re going to hit doubles and triples on? Don’t swing at them.’ As long as minor leagues are around, you’ll have guys at various stages of their development with various stages of command.”

When Thomas was in the minors, the organization asked him to focus on laying off inside pitches out of the strike zone, the kind that tended to lead to ground balls to the right side. He believes he has improved at that, but he has found that he still hits balls to second base on certain inside pitches that are actually in the zone.

Still, there are signs of progress. A sequence during an at-bat last weekend in Pittsburgh stands out. After chasing an inside slider, swinging through it, he fouled off another similar pitch, then laid off an inside fastball. On the seventh pitch of the at-bat, he got a slider over the plate and sent it out to right-center for a home run.

For Mather, it was a “perfect” at-bat. Thomas spoiled a tough pitch. He did not bite on another. But he also stayed true to his strength rather than being hyper-focused on addressing a weakness.

“I think if he was thinking 'in,'” Mather said, “that at-bat would have been over prior to that.”

Thomas believes his best approach at the moment is a combination of laying off those tough pitches early in counts and spoiling them after he gets to two strikes, but he also is continuing to work to get better at elevating those pitches.

“I think the ground balls that I’m hitting at 100 (mph), or whatever it is, to second base, I feel like those at some point will turn into in the air,” he said. “As of right now, I’m still working on it. This is what, my 20th-something game, so I think I’ve got some time."

The Diamondbacks seem to understand the importance of patience. Dipoto, for one, is trying to keep it at the front of his mind as he watches his young core of players try to acclimate, especially after missing so much time due to the pandemic.

“I really do think,” Dipoto said, “that somebody will make big, big mistakes if they give up on this group of prospects too soon.”

Reach Piecoro at (602) 444-8680 or nick.piecoro@arizonarepublic.com. Follow him on Twitter @nickpiecoro.