The jump from the Florida State League to the Eastern League is viewed by some Phillies officials as one of the greater challenges for a young player, specifically a young starting pitcher. It is a jump from a pitcher's league to a hitter's league. The weather is colder. The stadiums are smaller, the crowds bigger.

"The hitters are better," lefthander Cole Irvin said. "They're more patient. The strike zone is a little bit smaller. But it's supposed to be that way because you're trying to get ready for the big leagues."

That is what makes the potential rotation at double-A Reading one of the more fascinating units to follow in 2018. The Phillies have pursued pitching help this winter through trade talks and free-agent negotiations, but that pursuit has not yet produced a solution. It could be the Phillies acquire a stopgap arm to help an unproven rotation this season without addressing the long-term issue they face. An answer could materialize this July in the form of a trade or next winter in a trade or signing.

But the club's overall plan for contention in 2019 and beyond would benefit from another mid-rotation arm or two emerging within the farm system.

Irvin, a 2016 fifth-round pick who turns 24 this month, was the first to graduate A-ball and reach Reading. He could be joined there this year by Franklyn Kilome, JoJo Romero, Ranger Suarez and Seranthony Dominguez. There is decent potential among that group, with the caveat that anything can happen to a twentysomething starter with no experience above A ball.

All five of those pitchers are in Philadelphia this week as part of the Phillies' annual prospect seminar. The weeklong program includes sessions with team executives, a trip to the MLB Network studios, a few workouts, media training, and a Villanova basketball game. The prospects will hear from manager Gabe Kapler, pitcher Jerad Eickhoff and former Phillies like Larry Bowa, Larry Andersen and Brad Lidge.

The team typically invites players on the cusp of reaching the higher levels of their system. Kilome, Suarez and Dominguez were added to the 40-man roster this winter. All nine prospects invited are pitchers — the Phillies have promoted a sizable amount of position-player prospects to the majors and believe pitching is the strength of the next wave.

The current big-league rotation options are muddled; many of the young starters have not established themselves as anything beyond a No. 4 or 5 starter. One or two could improve their standing in 2018. But, barring drastic improvement, it will be difficult to flip those projections.

Therefore, the premium on developing a mid-rotation starter is warranted. And Reading is a great test for a pitcher who whizzed through A-ball. Last season, the Eastern League ERA was more than a half-run higher than the Florida State League's. Reading is regarded as a hitters' haven.

It can separate a real prospect.

Kilome, 22, is the most touted among the bunch that could begin at Reading. His lanky 6-foot-6 frame has led to inconsistencies in his mechanics, but when right, he possesses an imposing arsenal. The Phillies were aggressive with him in 2017, pushing him to Reading for his final five starts of the season.

"I learned a lot from last year," Kilome said. "It's different. The zone is a little smaller. You have smarter hitters. You have to executive your pitch, the right pitch. If you miss, he's going to kick your [butt]."

Dominguez, 23, is a hard-throwing righthander who could transition to the bullpen this season because of his potent fastball-slider combination.

Irvin, who is not a hard thrower but walked just 6 percent of batters he faced in 2017, has prepared some of his teammates for the jump. Yes, more mistakes will be noticed. But …

"It wasn't that drastic of a jump," Irvin said. "I've talked to JoJo Romero and a couple of other guys who will probably start in double A about that. I'm excited for them to take it head on and have a better start than I did."

Both Romero and Suarez began 2017 at low-A Lakewood and posted minuscule ERAs and walk rates. That earned them promotions to high-A Clearwater. Both are lefthanded, a real need in the Phillies' rotation. Both are confident.

"It's keeping everything simple," Romero, 21, said. "Not getting so caught up in, 'Oh you're moving up, these hitters are going to be so much better.' It's just trying to stick to what you do best. Focus on yourself. Better your craft. Ultimately, that will help you progress."

"I feel really good about the control of my pitches," said Suarez, 22, who has 67 walks in 326 2/3 career minor-league innings. "I don't think I can ask for anything else. It's very important for a pitcher to have control of his pitches."

With the same progress in double A, any of the young pitchers could emerge as real pieces for the future.

"The way they pitch," Kilome said, "it could be a really nice rotation."