Sox pitcher Julian Tavarez, who turned in a stellar relief effort, races to cover on a grounder to first base.

The Providence Journal / Bob Breidenbach

BOSTON — As Delmon Young’s first pirouette morphed into a second deep in the right-field corner, Jonathan Papelbon climbed onto the rail that fronts the Red Sox dugout and held his breath.

When the high fly off David Ortiz’s big bat ticked off a fan for a game-winning home run and a 5-4 victory, Papelbon and the usual sellout Fenway Park crowd exhaled and began a Boston baseball party that may not stop until the New York Yankees hit town tomorrow for a critical weekend series.

Papelbon, who ended a superlative night by the bullpen that featured five-plus innings of shutout relief, picked up his first win of the season.

“We’ll take that win and going into this (Yankee) series with the momentum is so big,” Papelbon said. “That’s one of the biggest wins of the season for us.”

While the 10th walk-off home run of Ortiz’ Red Sox career will deservedly garner the most praise, the job Papelbon and three other relievers did in picking up Jon Lester was equally as vital.

Lester struggled for his 3 1/3 innings, allowing four first inning runs and eight hits. After throwing a whopping 93 pitches, Lester left with the Sox trailing, 4-3. That’s when bullpen coach Gary Tuck turned to Julian Tavarez and issued a challenge.

“Gary Tuck said to Tavarez ‘If you keep this game tight, we’ll win the ball game,’ ” Papelbon said. “It all started with Tavarez.”

Tavarez responded by not giving up a hit and throwing three shutout innings. Manny Delcarmen, working on just four hours sleep after the birth of his first child (a boy), stepped in and scratched out the final out of the seventh inning and two more in the eighth. Hideki Okajima got the final out of the eighth when dangerous Carl Crawford struck out.

“Okajima picked me up there in the eighth,” said Delcarmen. “Guys are pulling each other up with our staff right now, which is huge.”

Papelbon came on in the ninth to face the meat of the Tampa order. Relying on his mid-90’s fastball, Papelbon got Carlos Pena to ground out to first and B.J. Upton fouled out to catcher Jason Varitek. Delmon Young then slapped a hard grounder in the hole between first and second. Dustin Pedroia dove to his left, stabbed the ball and made a quick throw to just nip Young.

“I’m thinking if (Pedroia) dives and makes a play, we can go get them in the ninth. That stop gave us a lot of momentum,” said Papelbon.

Tampa Bay closer Al Reyes, who’d blown just two saves this season, made the critical mistake of walking leadoff hitter Julio Lugo. Pedroia flied out to left for an out but that brought up the always-dangerous Ortiz. He lofted a Reyes fastball on a high arc to right field but the Ray’s Young seemed to be settling under it. As he drifted to his left, Young turned and went back to the left. Then he turned again and Ortiz’ fly settled into the hands of a fan in the first row of the stands.

“I thought (Young) had a shot at it,” said Tampa manager Joe Maddon. “That ball was really high and it just floated back towards the middle of the field. I think if he had been able to get to the right spot he probably would have been able to catch it.”

Papelbon led a charge onto the field to mob Ortiz at the plate.

He says it’s clear that even with injuries that sidelined Manny Ramirez and Mike Lowell last night, the Red Sox have the depth and confidence to keep winning games. Those are two traits that should come in handy when the red-hot Yankees (seven straight wins) come to Fenway this weekend.

“That’s the biggest thing, that we’re happy we still have a five-game lead going into this series,” Papelbon said. “Keeping that momentum, that’s absolutely huge for this ball club.”

kmcnamar@projo.com