In the span of three days, the Padres twice watched their presumed Game 1 starter leave his final regular-season start due to injury.

It’s been a rough week for the San Diego rotation.

With Mike Clevinger already on the shelf, right-hander Dinelson Lamet exited Friday's 6-5 walk-off victory over the Giants with what manager Jayce Tingler called “tightness in his biceps area.”

Lamet threw a slider to Evan Longoria in the top of the fourth inning before pausing and calling for athletic trainers. He was removed promptly, and after the game, Tingler expressed optimism that the injury might not affect Lamet’s playoff status.

“We'll know more information each day,” Tingler said. “But right now, the plan is for him to be able to make his start.”

Lamet joins Clevinger as Padres who had their starts cut short this week because of biceps tightness. Two days after Clevinger’s exit, he was formally diagnosed with a right-elbow impingement, and he received a cortisone injection on Friday. Clevinger has not been ruled out for the Wild Card Series, which begins on Wednesday at Petco Park.

Neither has Lamet, of course. But the Padres will have a better idea of his status later this weekend when he takes his first steps toward a potential Wild Card Series start.

“He’s feeling pretty good right now,” Tingler said. “We'll know more probably tomorrow and then the next day after he throws.”

Lamet’s impact is tough to overstate. The right-hander throws fire and pairs it with one of the sport’s nastiest sliders. He’s been the Padres’ most dominant pitcher by far this season. Lamet finished the year with a 2.09 ERA, which -- yes, it’s a short season -- ranks as the best qualifying mark in franchise history.

Until Wednesday, Lamet was lined up to start Game 2 of the Wild Card Series, but Clevinger’s injury seemingly thrust him into the Game 1 role.

Now, the Padres’ best-laid rotation plans have been ripped to shreds.

They might have Clevinger. They might have Lamet. They might have both. And they might have neither.

On Friday afternoon, general manager A.J. Preller indicated that his roster decisions would likely come down to the final moments before Wednesday’s deadline. And that was before Lamet’s injury.

“Not just with Mike, but with the whole group we’ll have some tough decisions and tough calls,” Preller said. “We’ve got some time.”

Three days ago, Chris Paddack was a fringe roster candidate. Now, the right-hander is almost certainly lined up for a first-round start -- and potentially Game 1, if Lamet misses time. Paddack also started Friday and was hit hard, allowing five runs over 3 2/3 innings in a Game 1 loss.

It’s been a roller-coaster second season for Paddack, who has been maddeningly inconsistent, mixing strong starts with duds. The Padres probably would’ve preferred to avoid that kind of volatility in a three-game Wild Card Series. They might not have a choice now.

Zach Davies, arguably the Padres’ steadiest starter, is expected to pitch one of those three games as well. The Padres would love to fill out that group with either Clevinger or Lamet. But if they are unavailable, Garrett Richards, Adrian Morejon, Luis Patiño and Joey Lucchesi -- who have been working out of the bullpen lately -- are also options to make shorter starts.