Rojas was 107th in Kiley McDaniel's top 200. Conrad, Kepley and Rojas all made BA's next 20 prospects just outside their top 100. So those are the 3 most likely to prop up the system going forward and none of them are likely to graduate in-season. Hartshorn is the next most likely guy. He was ranked in the top 75 draft prospects in a few places and has the type of power that really could easily make a top 100 list.
Those are the 4 guys who are currently in the organization and played domestically last year that I think can crack a top-100 list in 2026.
Other guys you mentioned - I'm not sure Southisene can every move up a lot in a single year because he needs to show he has the power to survive at every stop. Mathis could definitely bump up with a healthy season; he had good draft pedigree. I really liked Erian in 2024 when he was more 94-96. Last season, he was more 92-94. All that said, I think he's still a top 20 prospect in the organization.
A few other names I think could be good breakout candidates: Cabada, Cepeda, Lumpuy, Reid and Wing. This org really needs Reid and Wing to both show something this year, the pitching is horrible behind Wiggins.
EDIT: One name Bryan Smith has mentioned to watch is 2025 draftee RHP Nate Williams.