HOUSTON -- As if the Astros’ rotation wasn’t already going to be tested enough without its best arm, it’s quite possible Houston could be down another starter for the rest of the American League Championship Series.

Hours after Lance McCullers Jr. spoke for the first time since being left off Houston’s ALCS roster, promising rookie Luis Garcia exited Game 2 with a right knee strain Saturday with no outs in the top of the second inning during a 9-5 loss at Minute Maid Park.

When he departed, Garcia had just walked Kevin Plawecki on four pitches, all fastballs clocked at 90-92 mph, well below the 95.7 mph he maxed out at in the first inning and the 93.3 mph he averaged during the regular season. Things were already spiraling for the 24-year-old in that opening frame, when he struggled to pound the strike zone with effectiveness, allowed a double and walked two to load the bases and then surrendered a grand slam to J.D. Martinez.

Garcia’s knee issue is related to his push off from the rubber -- and one he has been dealing with for a period, manager Dusty Baker said after the game. But the right-hander hadn’t informed the team of the matter until after catcher Martín Maldonado noticed it and immediately called for Baker and head athletic trainer Jeremiah Randall. 

“It came to our knowledge that this has kind of been bothering him a little bit on and off, but he hadn't said anything about it,” Baker said. “It wasn't bothering him enough not to pitch.”

Jake Odorizzi, who was added to Houston’s ALCS roster after not being included in its AL Division Series contingent, took over for Garcia, whose status moving forward is unclear.

Odorizzi was slated to pitch Game 4 on Tuesday, Baker said, but that plan is probably no longer an option after the veteran tossed 82 pitches over four innings. Odorizzi also surrendered a grand slam, to Rafael Devers in the second inning, that essentially put Game 2 out of reach for the Astros before it really got going.

Now the series shifts to Boston -- and the Astros must figure out how to cover a mountain range of innings. Their bullpen has accounted for 14 1/3 of the 18 innings this series, with all but Zack Greinke having made an appearance.

Is this sustainable?

“I don't know,” Baker said. “We've called upon them a lot, but that's kind of modern baseball, too. When guys aren't conditioned really in modern baseball, six or seven innings, it does put pressure on you.”

The Astros can recall a number of pitchers on their taxi squad to replace Garcia -- the most likely candidates are right-handers Peter Solomon or Brandon Bielak -- but if they do so, Garcia would not be eligible to return for the World Series roster if the Astros advance.

Essentially, everything beyond José Urquidy starting Game 3 on Monday at Fenway Park is up in the air now that Odorizzi is likely unavailable for Game 4.

“I don't think I'll probably be able to start that game now,” Odorizzi said. “I don't think that's much of a secret, but, hopefully, I'll be able to contribute soon around that time and do everything I can to bounce back quickly.”

Back to Greinke -- given that the Astros included him on their ALCS roster, they’ll use him at some point. Baker said that the six-time All-Star is stretched out to 40 pitches coming back from an IL stint three weeks ago due to neck soreness. Greinke has pitched one inning of relief in this postseason.

If the Astros were to use Greinke, it likely would be as an opener in Game 4. It’s almost certainly why Greinke didn’t pitch on Saturday, especially given the wide scoring margin.

The 37-year-old hasn’t been all that effective, either, in the final season of a six-year, $206.5 million contract. In the second half, he had a 5.34 ERA, and opposing hitters tagged him for an .802 OPS.

As for Garcia, the breakout rookie is already well past his previous professional high mark for innings pitched, at 159 after topping out at 108 2/3 in 2019 in the Minors. This is something the Astros have been cognizant of since well before the All-Star break, when they began more closely monitoring his workloads. He has thrown more than 80 pitches just three times after Aug. 24.

His start on Saturday marked the shortest postseason outing by a starter in Astros history.