When the Padres broke camp and left for San Diego on Monday afternoon, they left one of their best pitchers off the Opening Day roster -- by design, of course.

It has been clear for several weeks now that Dinelson Lamet wouldn't be ready in time for the season opener on Thursday. The hard-throwing right-hander sustained an elbow injury last September, and the Padres have been very cautious in building him up this spring.

Lamet made his second Cactus League start on Monday at Peoria Stadium, allowing a run over 1 1/3 innings in the Padres' 10-2 loss to the Rockies before he reached his pitch count. It marked the first time Lamet has thrown more than an inning in game action -- an important step in his slow, but steady progression.

• Padres: 'We're built to win a championship'

“Every day that he’s able to build up and get more game innings, that’s a positive,” manager Jayce Tingler said.

Lamet will travel with the team for Opening Day in San Diego, where he’ll throw his next bullpen session. Then he’s slated to return to Peoria, Ariz., to continue his buildup. He feels his Spring Training couldn't have gone much more smoothly.

"Ideally I'd be breaking with the team," Lamet said. "I always want to be with that group and help them the most that I can. But at the same time, when it's a matter of health, I understand why I'm staying back. ... I know that I'm going to be ready. That's the thing that matters most for me. To be ready, I need to be healthy."

The Padres never publicly disclosed the specifics of Lamet's injury, but he said he avoided Tommy John surgery by shutting things down just before the playoffs last season.

Lamet has not eclipsed 100 innings in a season since 2017. Given that and the September injury, the Padres were never going to ask him to handle the workload of a full season -- plus, potentially, a postseason.

The Padres haven’t unveiled all the specifics of their plan for Lamet. It remains unclear when he might be ready to begin the season. A late April return still seems possible, but the Padres have made it clear they aren't going to rush him back. For now, Lamet will remain in Peoria facing Minor League hitters in game-like settings.

As for his start Monday, well, it certainly wasn't vintage Lamet. He struggled to command his fastball and allowed a run on two hits and a walk.

"I'm not too worried about it," Lamet said. "Again, I haven't faced hitters for so long. I think so much of this process is just getting used to that again."

Most important, Lamet worked into a second inning with no issues and no noticeable dip in velocity. He threw a handful of sliders, as well -- perhaps the most aggressive he has been with the pitch since the injury. The next step for Lamet will be to work past the strict 30-pitch limit that has been set for him lately. (He threw 29 pitches in both of his multi-inning outings – once on a back field and again on Monday.)

"It was important for me to throw two innings," Lamet said. "That was the goal here. I was able to come out of that second inning feeling pretty good. Again, I'm just trying to leave these outings healthy, and I was able to do it."