On the final pitch that Carlos Martínez threw Wednesday night, he fell off to the first-base side of the mound and grabbed his left side. He exited soon after, putting his immediate future in question and leaving the Cardinals in a tough spot.

Martínez left the game with a left mid-back strain, the Cardinals announced. Manager Mike Shildt had no further update after the game, but the right-hander likely will have imaging done before determining the next steps.

The damage on the field was done before Martínez left, and the Royals kept pouring on in the Cardinals’ 12-3 loss at Kauffman Stadium. The series loss against the intrastate rival was a disappointing end to the Cardinals’ longest road trip of the season, and the loss left the club 7-6 on that trip.

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On Thursday, the Cardinals return home to Busch Stadium for the defining final stretch of games: a five-game, four-day series against the Brewers, who are chasing the Cardinals in the National League Central standings and lost to the Reds on Wednesday.

“We just came off a 13-game, 10-day road trip with a winning record,” Shildt said. “We have to feel good about that, and we’ve got our destiny in our own hands. I do feel good about it.”

The Cardinals are going into this series with a handful of questions. One is the ongoing struggle to score runs -- the Cardinals were held to one run through eight innings Wednesday before Harrison Bader’s two-run single in the ninth showed some encouraging life. The Cardinals hit just .201 on this road trip with seven home runs.

In eight games, they had one hit or less with runners in scoring position, and they won two games without a hit with runners in scoring position. The defining at-bat of Wednesday’s game was in the sixth inning with the bases loaded and two outs. Royals lefty Danny Duffy was pulled for right-hander Scott Barlow, and Shildt called on Brad Miller to pinch-hit. Down five, the Cardinals had a chance to gain momentum, but Miller grounded out.

The second question is the health of their rotation. Kwang Hyun Kim, Jack Flaherty, Daniel Ponce de Leon, Adam Wainwright and Austin Gomber are all scheduled to pitch this weekend. Win the series, and the Cardinals are in the postseason. Lose it, and there’s a chance the Cardinals will have to travel to Detroit on Monday -- extending the regular season -- to make up one or two of the postponed games from earlier this season. Those games would only be played to determine if a team gets into the playoffs or if the Cardinals could become the home team in an NL Wild Card Series as a top-four seed.

The Cardinals will need at least one starting pitcher if they play Monday. Martínez (0-3) will be in turn for it -- but his performance Wednesday and injury suddenly puts that schedule in doubt.

“We’ll cross that bridge if we have to cross it,” Shildt said.

Royals catcher Salvador Perez crushed two home runs in his first two at-bats against Martínez. The first was a two-run shot in the first inning on a slider up in the zone. The second was a three-run home run in the third on a changeup that eased down instead of biting. The two averaged 436 feet, according to Statcast. Martínez, who was not available after the game, was ultimately charged with eight runs on nine hits.

Until Wednesday, the former All-Star stayed healthy through the winter, the spring and the summer to earn the opportunity to secure his spot in the rotation. With it, Martínez showed glimpses of success. But he also searched for the efficiency necessary to keep his spot.

“He made the most of his opportunity to earn his spot,” Shildt said. “He just never really got into a groove. Carlos is a little bit of a rhythm pitcher. He gets in the feel, in that groove, and when he does, it’s lights out. He showed flashes of it … but he never really ultimately was able to get any consistency going with his pitches.”