With the Houston Astros facing mounting injuries in their starting rotation, Manager Joe Espada has pulled back the curtain on the organization’s next wave of talent—three standout pitchers who could make their MLB debuts this summer. According to team sources and Espada himself, Miguel Ullola, Brandon Walter, and Alonzo Tredwell are firmly in the conversation for call-ups in the coming weeks.
Miguel Ullola – Triple-A Sugar Land
Ullola, just 22 years old, is one of the most exciting arms in the Astros’ system. The Dominican-born right-hander has consistently impressed in his first full season at Triple-A, flashing a fastball that hits the upper 90s and a wipeout slider. In 10 starts for the Space Cowboys, Ullola owns a 3-2 record with a 3.55 ERA, 45 strikeouts, and 21 walks over 33 innings pitched.
He was recently named Pacific Coast League Pitcher of the Week, and scouts praise his improved command and mound presence. With Houston losing starters Hayden Wesneski and Ronel Blanco to Tommy John surgery in recent weeks, Ullola could be one of the first reinforcements to get the call.
“Miguel’s growth has been remarkable,” Espada said. “He’s not just throwing hard—he’s pitching with purpose now. He’s on our radar.”
Brandon Walter – Triple-A Sugar Land
Walter, 26, made his first MLB appearance for the Astros this season, delivering five shutout innings with five strikeouts in a spot start against the Tampa Bay Rays on May 20. The left-hander, acquired from the Red Sox organization, has been sensational in Triple-A, posting a 3-1 record and 1.94 ERA over 11 games (seven starts). He’s struck out 49 batters and walked just seven across 47.2 innings, holding opponents to a .177 batting average.
His performance, consistency, and major league readiness make him a likely option for the Astros’ rotation should injuries persist.
“Brandon already showed he can handle the big stage,” Espada noted. “He’s the kind of depth every team wishes they had.”
Alonzo Tredwell – Class A Fayetteville
Though he’s at a lower level of the minors, Tredwell is quickly making a name for himself. Drafted in the second round in 2023, the 23-year-old righty has bounced back from a rough pro debut with a strong start to 2025. Recently named Carolina League Pitcher of the Week, Tredwell threw five no-hit, scoreless innings with four strikeouts in his last start.
On the season, he’s 2-0 with a 3.06 ERA, 39 strikeouts, and 14 walks across 35.1 innings. While a promotion to High-A Asheville is likely the next step, the Astros are keeping a close eye on his rapid progress.
“Alonzo’s made real strides,” said Espada. “He’s got the kind of makeup you look for in a future starter.”
Looking Ahead
While the Astros’ minor league system hasn’t received much acclaim in recent years, internal development continues to be a strength. These three pitchers represent the next wave of homegrown talent—ready to contribute in a season where depth is more important than ever.
As the club battles to stay competitive in the AL West and cope with roster challenges, fans should not be surprised if all three of these names appear in an Astros uniform before the summer is over.
