"We weren't sure if it was going to be a thing that he could work through quickly, but after the doctor saw him [Monday] night, he made the determination he needs to take some time off and let it heal," general manager Jeff Luhnow said. "It's unfortunate, because we felt like he was a couple of days away from rejoining our team and clearly is a missed presence in the lineup and in the outfield. We're going to have to wait until he's completely healthy. We don't want to take any more risks."
Springer played three games on a Minor League rehab last week in Class A Quad Cities and tweaked his quad running the bases.
Springer made his much anticipated Major League debut in mid-April and took off in May, being named American League Rookie of the Month. He's played in 78 games, hitting .231 with 20 homers, 51 RBIs and a .336 on-base percentage.
"It's tough, just because I'm a competitor and I want to go out there and help the team, but I've got to get healthy and see what happens," Springer said. "I want to go out there and compete with these guys and be able to help and not be a cheerleader. I want to be able to play, but you've got to be smart."
Springer will travel with the Astros on Wednesday night before they open a 10-game road trip on Thursday at Fenway Park against the Red Sox. Springer, who's from Connecticut, grew up a huge Red Sox fan, but won't get the opportunity to play in Boston.
"It'll be tough, but I think it's harder to not play in general," he said. "It's not just because we're going to play in Boston and all that stuff. I want to play every day here."
Springer remains confident he'll get on the field again this year.
"That's the ultimate goal is to get back out there," he said. "I'll get stronger and keep doing what I've got to do in order to play."
Luhnow believes Springer will play most of September.
"This type of injury, he should be able to come back from," he said. "Obviously, we're going to be very cautious with bringing him back, but we still have plenty of time. I expect he'll play the month of September here."
Losing Springer for an extended time was softened by the news Tuesday that outfielder Dexter Fowler would return Wednesday for the first time since June 26. Meanwhile, outfielder Alex Presley is also close to returning.
"Obviously, losing George Springer is a big void for our ballclub," manager Bo Porter said. "He is a player that can impact a game in so many ways. We missed him the entire time in which he's been out already, and we will continue to miss him. At the same time, the guys that are going to have the opportunity to get that playing time, they can use the opportunity to take advantage of it."