Sept roster expansion accelerates a wave of rookies and returnees across MLB fantasy rosters. Mets promote Jonah Tong and Nolan McLean to help a six-man rotation down the stretch; Boston tab Payton Tolle to stabilize a rookie-heavy brood. Cincinnati’s Sal Stewart and Kansas City’s Carter Jensen arrive with multi-position upside, while Miami’s Connor Norby and Arizona’s Jordan Lawlar return from injuries and search for steady at-bats. The Reds also lean on Sal Stewart for spark while Perdomo’s extension with Arizona locks in infield predictability.

Risers collide with risk as first-timers settle in: Tong’s debut win over Miami signals potential multi-start value; Tolle impressed enough to stay in the rotation through September; Norby and Lawlar offer speculative upside in shallower formats; Ke’Bryan Hayes’ move (via trade context) and Perdomo’s extension shape the infield depth for late-season fantasy planning.