WEST PALM BEACH, Fla. -- From the time he reported to Spring Training through his start against the Nationals on Wednesday, very little in Lance McCullers Jr.'s immediate orbit had changed.

He's healthy and on track to return to the Astros' active roster, after a year off rehabbing from Tommy John surgery. He's being closely monitored by his coaches to make sure the transition continues to go smoothly. He's mostly throwing free and easy, building innings and confidence with each trip to the mound.

The only thing that has changed, really, is McCullers' place in the pecking order of Houston's starting rotation. He was the presumed No. 3 starter. Now he's moved up a spot, in the wake of the right lat strain that will delay Justin Verlander's regular-season debut.

The Astros will be counting on McCullers, even with a probable innings limit, to add stability to a rotation that is in transition and saddled with uncertainty.

"Thankfully, from what I know and what I've heard, it's a minor thing -- that's very fortunate," McCullers said of Verlander's injury. "He's definitely the horse of this rotation.

"I can't make up what Verlander would give to this team, but hopefully he's not gone long, and hopefully I pitch well not just the whole year, but definitely well in his absence."

McCullers is in the process of building innings with an eye toward Opening Week. He threw 50 pitches over two scoreless innings in the Astros’ 6-2 loss to the Nats on Wednesday, exiting the game following a leadoff walk to Andrew Stevenson in the third. The 26-year-old struck out three, allowed one hit and one walk, threw 31 strikes and hit 93-95 mph with his fastball. McCullers said he was encouraged by the quality of his changeup.

"I'm very happy with the velo and happy with the way I'm able to move the fastball around, with the changeup early -- swing-and-miss changeup," he said. "I couldn't ask for anything more except maybe being a little more efficient with my pitch count."

McCullers is on track to be fully stretched out when the season starts, and as it stands, he's in line to start the second game of the season on March 27 vs. the Angels, though the rotation order is still to be determined. With Verlander out, Zack Greinke will likely start the opener and Jose Urquidy would presumably slide into the No. 3 slot, followed by two of the four candidates being considered for the final two spots.

McCullers, who was a rising star in Houston's rotation when he famously threw nearly two dozen consecutive curveballs in the Astros' pennant-clinching win over the Yankees in 2017, should provide stability in an area where there is a shortage of depth.

His outing Wednesday, while not perfect, was an important step.

"The fact that he didn't labor at all -- he was coming out hot, coming out good and coming out easy," manager Dusty Baker said. "That's very encouraging. For a guy that hadn't pitched in a long period of time, he was pretty sharp."

The only issue will be the unavoidable innings limit, which is standard for a pitcher returning from Tommy John surgery. A hard number is difficult to determine, but it’s unlikely McCullers will exceed 150 innings for the year. There will be off-days and segments of the schedule that can be manipulated so that he can maintain a reasonable workload, and he hopes to still be very much part of the rotation mix in the latter stages of the regular season.

Pitch counts and innings limits are coming, but McCullers vowed not to let that cloud his mind when he’s pitching.

"I'm not going to spend my whole game staring up at the scoreboard like, 'My gosh, my pitch count's rising,'" he said. "If the wolf is hungry, he's gonna eat."