Tanner Rainey allowed three runs in the eighth inning of a 5-0 loss to the Minnesota Twins on Tuesday night. (Jim Mone/Associated Press)

MINNEAPOLIS — Dave Martinez ran the calculations, he consulted his pregame plan, and when the Washington Nationals manager made his decision Tuesday night, in a big spot of a tight game, he landed on Tanner Rainey.

The Nationals trailed the Minnesota Twins 2-0 heading into the bottom of the eighth. Once Rainey exited, the bases loaded behind him, they were down 4-0. Once the inning was over, after Javy Guerra yielded a sacrifice fly, it was 5-0 and the Twins were coasting to a victory by that score. Martinez had warmed up Hunter Strickland an inning prior. The Nationals hadn’t played Monday, meaning each of their relievers was rested, and Martinez had only used Wander Suero and Guerra in a lopsided win over the Atlanta Braves to finish the weekend.

All of his options were on the table. Washington was in striking distance of a first-place team. But by putting in Rainey, an atypical high-leverage reliever, Martinez showed the balance he has to strike in the coming weeks: The Nationals, as leaders of a tightening NL wild-card race, have to be vigilant to the end of every game. But they can’t blow out their best arms in the process.

“These other guys, they got to pitch,” Martinez said, lumping Rainey into the group of pitchers not named Daniel Hudson, Strickland, Suero, Sean Doolittle or Fernando Rodney. “They have to do their job. We need them all right now. If it’s a tie or something, it’s different.”

What Martinez was saying, not so subtly, is that the moment wasn’t quite big enough to fire one of his bullets out of the bullpen. That could be contested, especially given the way the Chicago Cubs, Milwaukee Brewers and others are closing in on Washington. But that was his logic, take it or leave it, and did indicate a shift in approach.

Earlier this season, when the Nationals were struggling through spring, or when they were trying to erase a 19-31 start at the beginning of summer, Martinez rarely showed restraint with his relievers. That’s what led to such a heavy workload for Doolittle, who ultimately needed two weeks to rest his arm in August. That’s what led Martinez to use Rodney three times in two days, a risk that backfired in the end. And that’s what has Suero at a team-high 69 appearances, 12 more than the next-closest pitcher, with 19 games left to play entering Wednesday.

There was an argument then that Martinez should have eased off the gas a bit. The Nationals flipped a switch in late May and became one of baseball’s better teams. Putting Doolittle in with a four-run lead, or pitching Suero for a third straight game, could have seemed unnecessary when guys such as Guerra, Matt Grace or Tony Sipp hadn’t pitched in the past week. But another view is that that was needed for Washington to save its season. The bullpen was on a historically bad pace then. And the results, putting the Nationals in control of their playoff chances, back Martinez up.

But here the Nationals were Tuesday, still alive in Minneapolis, in need of three outs to give the offense a puncher’s chance. Their bats have erased late deficits all year. The bullpen got deeper at the trade deadline, once Washington acquired Hudson, Strickland and Roenis Elías in trades. Elías, the club’s only other left-handed reliever aside from Doolittle, is out with his second hamstring strain since Aug. 2. Everyone else was good to go for the series opener against the Twins, but that’s when Martinez was cautious with his usual pitchers for the seventh, eighth and ninth.

If there were a loose bullpen depth chart, based on how Martinez has used his relievers in the past month or so, Rainey would be sixth behind Hudson, Doolittle, Strickland, Suero and Rodney. Doolittle is working back to the closing role and, again, is the only healthy lefty at the moment. Hudson has had the ninth inning in his place. So Strickland, Suero and Rodney theoretically could have pitched the eighth Tuesday instead of Rainey.

Martinez stayed away from Hudson because he warmed up every day during the four-game series in Atlanta. He wanted to give Suero, overworked all season, two full days of rest. And he has been careful with Strickland because the right-hander missed most of the first four months of the season with a strained lat muscle. Rodney, 42, pitched in two of the four games against the Braves. Rainey, when accurate, is a more-than-capable reliever. He has a high-90s fastball, sometimes reaching triple digits, and a devastating slider. He is just erratic way too often. He is striking out 13.6 batters per nine innings in his first full major league season. He is also walking 8.1.

Rainey hit leadoff hitter Jonathan Schoop, and it was downhill from there. He gave up a single and a double, struck out Nelson Cruz and finally walked the bases loaded before he was hooked. He wore his mistakes after the game, speaking bluntly about what went wrong and, most importantly, acknowledged that he has to find a way to get outs when he is not at his best.

“It’s definitely something I have to figure out,” Rainey said. “You’re not going to have your best stuff every day and you have to be able to compete without it.”

But what he couldn’t control, from the start, is whether he should have been out there in the first place. Martinez figured a two-run deficit was the right situation for a secondary reliever, given the time of year and what the Nationals are playing for down the stretch. And decisions such as that, both now and for the rest of September, could hold a lot of weight.

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