TAMPA — This time it was only the fifth starter who was injured.

Next time it could be much worse for the Yankees’ house-of-cards rotation.

Starter Chris Capuano made it past only one batter Wednesday before injuring his right quad covering first base in a 10-6 loss to the Red Sox at Steinbrenner Field.

He’s down and out.

Ten days into spring training games, the Yankees are already down one spot in their rotation. That is not a good start or omen.

It could be worse.

Masahiro Tanaka pitches in his first spring training game Thursday night against the Braves. If his damaged right elbow does not endure this season, the Yankees can kiss 2015 goodbye.

The Mets will win the arms race and the city. It’s that simple.

Manager Joe Girardi admitted it was nerve-wracking seeing Tanaka pitch last September when he came back from his rehab.

“When the first game started, I sat on the edge of my seat a little bit, but I feel pretty good about where he is at,’’ Girardi said.

Asked if he would be sitting on the edge of his seat Thursday, Girardi answered: “No, not like I did in September.’’

Don’t believe that for one second.

Every time Tanaka throws a pitch, the Yankees season could disintegrate.

CC Sabathia pitches in a simulated game Thursday afternoon. If all goes well with Sabathia, he will pitch in his first game Tuesday night. The Yankees have to hope his right knee can hold up under the strain. Sabathia has put back on his pitching weight and is letting it fly.

Everywhere you turn in the Yankees rotation, there is danger. They already have had the first crack in the armor and we’re not even to St. Patrick’s Day.

The Yankees are taking the huge gamble this rotation will survive.

They could go out and make a play for the Phillies’ Cole Hamels, who will be acquired by some team. The lefty will be an expensive difference-maker, but it appears the Yankees are committed to not trading any of their top young prospects.

A deal like this doesn’t get done if you don’t include Luis Severino and a young hitter.

The Yankees are rolling the pitching dice.

General manager Brian Cashman said he is not going to worry too much about Tanaka and Sabathia, their work on Thursday, and things he can’t control.

“It’s the next step in their progression,’’ Cashman said. “I’ve been in this job a long time and I used to sweat things that I couldn’t control. It’s not in my control if Tanaka stays healthy for 10 more years or 10 more days.’’

If it is 10 days, the Yankees can forget about 2015.

“If it declares itself in an adverse way, we are just going to have to deal with it and do whatever the next course of action is, which would be a surgery if he has a problem, but he’s been great,’’ Cashman said, his cup clearly half full.

“Everything has been as good as we can expect for all those guys thus far. This will be another step in the process.’’

About three hours after Cashman spoke, Capuano came up with his injury.

The Yankees have no room for error. They cannot afford to take a step back in the process with Tanaka and Sabathia.

“We need big things from those guys, but we need big things from a lot of guys,’’ Cashman said.

Tanaka came back last September for two starts and the second one was dreadful, but the elbow survived.

It will be interesting to see where Tanaka’s velocity will be Thursday night.

“We’re pretty happy where he is at, but we need to build him up now,’’ Girardi said. “It was good that he started two games last year because I think there would have been an even bigger of a deal [Thursday].’’

It’s still a big, big deal.

This is a rotation for which everything must go right and something has already gone wrong.