Osuna, widely considered one of the best closers in Major League Baseball, has yet to face live hitting in summer camp as he works back into game shape.
The COVID-19 pandemic shut down spring training in March, and Osuna spent much of the off time in Mexico, where restrictions combating the virus prohibited an ideal workout routine.
Osuna, while on the 30-man Opening Day roster, likely won't pitch in the opener Friday when the Astros host the Seattle Mariners.
Pressly said pitching just an inning later should not affect his routing.
"I can't really speak for Osuna. I'm sure he's relatively close to getting ready," Pressly said. "My routine won't really change. It's just pitching one inning later. I've done it before, so it's nothing really out of the ordinary for me. It's just you've got to minimize the mistakes when you're in that ninth-inning role and Osuna does that probably better than anybody.
"But it'll be nice once we get him back on the mound and pitching for us in that ninth. But until he gets back, I'll just dp whatever this team needs me to do."
Osuna has spent most of his time at camp throwing long toss, at which Baker said he's one of the best he's ever seen, and running wind sprints to improve his cardiovascular condition.
Through 60 games last season, Osuna recorded 16 saves with a 1.98 ERA, 0.66 WHIP, .450 OPS.