Boston’s Mike Lowell, who was named Series MVP, slides in just ahead of the tag by Colorado catcher Yorvit Torrealba in the fifth inning last night with the Red Sox’ second run of the game.

The Providence Journal / Bob Breidenbach

DENVER — It was clear when he came into last night’s game that, in Jonathan Papelbon’s mind, if the Rockies were going to beat him, they were going to have to beat him on his best pitch — the fastball.

And despite a couple of heavy-duty scares, Colorado wasn’t up to the challenge as Papelbon and the Red Sox held on for a 4-3 victory and a sweep of the World Series for Boston’s second crown in four years.

Papelbon ended the game by sizzling a 94-mph heater past pinch-hitter Seth Smith for a game-ending strikeout and then threw his glove high into the air as catcher Jason Varitek rushed out to the mound and jumped into Papelbon’s arms.

The right-handed flame-thrower entered the game in the eighth with one out, none on and Boston on top, 4-3, only five outs away from winning the World Series.

He threw 12 pitches in the eighth. The first 11 were fastballs, ranging from 94-96 mph. That netted him a groundout and a 1-and-2 count on Ryan Spilborghs. He tried to fool Spilborghs with his next pitch, a changeup at 88 mph. Spilborghs put a charge into it, sending a deep drive to center.

The Sox and their fans held their breath, but Coco Crisp ran the ball down for the catch in deep center.

In the ninth, Papelbon threw 11 pitches, nine of which were fastballs, most either 94 or 95 mph. The only two pitches that weren’t fastballs were an 0-and-1 splitter and a 2-and-1 changeup to Smith before the punchout, which followed a groundout by Yorvit Torrealba and a hold-your-breath fly out to the fence in left by Jamie Carroll.

Rested Lester in fine form

As Boston manager Terry Francona said several times heading into last night’s game, Red Sox starter Jon Lester had gotten past the point where he was thinking about the cancer scare he survived last year.

That, said Francona, wasn’t a concern when Lester was on the mound. In a game, said Francona, Lester is thinking only about the game, and what he has to do to hold the opposition at bay.

So Francona handed the ball to his 23-year-old left-hander last night in Game Four with the Red Sox one win away from claiming the World Series crown.

And Lester, making his first start in the postseason, competed. While Lester showed great maturity and presence on the mound, attributes that belie his relative big-league inexperience, he also was very successful because of the command he had with all three of his pitches.

Lester blanked the Rockies on three hits over 5 2/3 innings. His fastball was in the low 90s, his slider in the 82-85 mph range and his curveball was dropping in around 73 mph.

All three pitches helped him in his 92-pitch outing last night. He twice fanned Troy Tulowitzki, Colorado’s Rookie of the Year candidate, with biting sliders down and in. He whiffed Matt Holliday, the Rockies’ MVP candidate, with a high heater. And his curveball had Torrealba and Kaz Matsui way out in front for fifth-inning popups to shortstop.

In short, Lester had it all going for him despite not pitching for 11 days. It was an impressive performance for any pitcher, let alone a youngster only one year removed from a life-threatening health issue.

Francona’s move pays off

Mike Timlin overpowered Matsui and Tulowitzki, the Rockies’ top of the order, with a runner at first and the Sox up, 3-1, in the seventh.

So Francona had a decision to make. Should he pinch-hit for Timlin, who was scheduled to lead off the top of the eighth and turn to Hideki Okajima for the bottom of the inning, even though the left-hander had thrown 28 pitches on Thursday and 28 more Saturday night?

Francona opted to pinch hit for Timlin, sending up Bobby Kielty, who hadn’t appeared in the World Series and hadn’t swung a bat in a game since Oct. 18.

Kielty crushed the first pitch he saw from Colorado left-hander Brian Fuentes into the left-field seats, his no-doubt-about-it homer giving the Red Sox a little extra breathing room at 4-1. The switch-hitter, in the first World Series at-bat of his career, threw up his arms in triumph and pure joy about four steps out of the batter’s box.

And the breathing room proved vital.

skrasner@projo.com