The victory, coupled with the Yankees' 18-9 loss to the Angels, gives the Red Sox a six-game lead in the American League East.
The 26-year-old seems to be in a much better position this season than during his rookie campaign, too.
"[This year], I feel like I've got my legs, I've got my arms and less headache," said Papelbon, who saw his 2006 campaign end prematurely with a fatigued right shoulder in September. "Last year was a grind for me. I really grinded and grinded until I couldn't grind any more, and this year I'm knowing my body and the system better. ... I feel [very] near 100 percent at this part of the season."
A lot of things had to happen for Papelbon to be in line for the save, though, and the battle started with Andy Sonnanstine.
The Red Sox last saw Sonnanstine six days ago, when the rookie righty held them to three runs over 6 2/3 innings for the win. He stifled Boston's offense then, allowing just four hits during his watch and seeming to exude the confidence the Major League's best team lacked on that day.
The Red Sox were more than happy on Tuesday, as they exposed Sonnanstine's weaknesses away from Fenway Park.
Sonnanstine has used a variety of arm angles and deliveries to fool opponents this season, but knowing what to expect the second time around, and facing him for the second time in less than a week, gave the Red Sox an advantage.
"I think the first time you face somebody, the pitcher definitely has an advantage," Francona said. "Seeing them in person certainly has to help your comfort level, but that doesn't mean you're going to hit them."
On Tuesday night at least, that's exactly what it meant. The win pushed the Red Sox's record to 76-50, matching their second-best start in franchise history. Just four other times since 1951 has Boston won at least 76 of its first 126 games, including 1975 (76-50), 1978 (79-47), 1979 (76-50) and 1995 (76-50).
Opposing Sonnanstine on the mound was Jon Lester, who was saved from his inconsistency by a super-charged offense. Although the southpaw allowed the Rays to score five runs, he still walked away a winner thanks to one big inning.
Lester lasted just 5 1/3 innings and was hurt mostly by the long ball -- a three-run shot in the fifth and a two-run blast in the first amounted to the total damage. He threw 97 pitches, 54 for strikes, walked four and recorded four punch outs.
"At times I was really good, and at other times I was really bad. I don't know why," Lester confessed. "Luckily, bullpen picked me up ... [and] so did the offense.
"It was a good team win."
The Red Sox flexed their muscles in the fourth to bury the Rays in a hole too deep to climb from.
With the game tied at 2, David Ortiz singled. After Manny Ramirez struck out, Mike Lowell was struck with a pitch on his left hand to put runners on first and second. J.D. Drew singled to load the bases, and then Jason Varitek connected for a bloop single to score Big Papi and give Boston a 3-2 lead.
Coco Crisp added to the cushion with a two-run double to right field, and former Ray Julio Lugo followed suit with a double of his own to push the score to 7-2.
Each man in the Red Sox starting lineup finished with at least one hit.
"When you get something from 1 through 9 [hitters], it enhances your chances to win," Francona said.
Boston would need nearly all of those insurance runs by the fifth inning, when Akinori Iwamura took a full-count pitch from Lester and put it in the left-field bleachers for a three-run homer that brought the Rays back to within two.
"We kept coming back," Rays manager Joe Maddon said. "Aki's home run was big for us. We had opportunities, but that five-run inning is so hard to overcome. ... To score that many runs on that few hits is very quirky."
Also out-of-the-ordinary was Ortiz, who banged out his first triple since Sept. 8, 2006, in the first to push across a run. He scored a moment later on Ramirez's sacrifice fly to hand Boston a 2-0 lead out of the gate. The burly designated hitter also hustled to beat out an infield single in the fourth inning.
"He felt that triple for about five innings," Francona joked. "He can get going when he needs to. He had fresh legs. It's not fun to give guys the day off [Monday], but it really helps."
A critical error by Dustin Pedroia with two on and two outs in the seventh saw Tampa Bay claw back to within two. Pedroia botched a hard-hit liner from Carl Crawford that allowed Josh Wilson to scamper home from third.
Wilson was hit by a pitch from reliever Manny Delcarmen earlier in the inning, but otherwise the bullpen was concrete.
"My front side was real good, and my delivery was sharp," Papelbon said. "And I was staying behind the ball tonight. We ... came in and shut the ballgame down tonight. Hopefully that becomes a familiarity for us -- not that it isn't already, but hopefully we keep things going."