Dioner Navarro celebrates his game-winning single.

AP / Mike Carlson

ST. PETERSBURG, Fla. –– In the series opener here Monday night, Boston won a laugher over Tampa Bay, a game over almost before it began when the Red Sox raced out to a 3-0 lead after three batters.

Last night, however, was another story.

With an opportunity to secure first place for themselves, the Sox lost a 1-0 lead in the seventh, then lost the game in the bottom of the ninth on a bases-loaded, one-out single by Dioner Navarro for a 2-1 Rays victory.

It marked the third time in the last four meetings between the two teams that the Rays had won a game in their final at-bat. They did it twice in as many nights at Fenway last week, then did it again to reclaim sole possession of the A.L. East lead.

The win was Tampa Bay’s 11th walkoff triumph of the season.

“It’s amazing how one pitch can change the complexion of a game,” lamented Boston starter Josh Beckett, who was brilliant in eight innings, allowing only three hits.

Beckett had been perfect until Cliff Floyd singled with one out in the fifth, and shut the Rays out through the first six innings.

But Carlos Pena, who won a 14-inning marathon last week when he swatted a three-run homer to left, drove a first-pitch slider out to left.

“A poorly executed pitch,” said Beckett. “I wanted to throw it down (in the zone), but it was up. He’s strong –– you can’t leave a pitch up like that to him.”

In the ninth, with Beckett having exited after eight innings and 95 pitches, the Rays loaded the bases against Justin Masterson on an opposite-field bloop single by Jason Bartlett, a walk to Pena and a hit-batsman (Cliff Floyd).

With the Sox hoping for a double play, Masterson left a sinker up to Navarro, who drove it over the head of center fielder Coco Crisp, who had been positioned in shallow center.

“I was just trying to make something happen,” said Navarro. “I was trying to hit the ball up the middle. I’m glad I hit it hard enough and far enough for the run to score.”

“I’m disappointed we didn’t get through the inning,” said Masterson, “because Josh pitched such a great game. I wanted the sinker down, but it was up more than I wanted it to be. Obviously, that’s not what I wanted in that situation.”

“A lot of things happened in that inning,” said manager Terry Francona.

In addition to giving the Rays a one-game lead in the standings –– two in the loss column –– the victory served to give Tampa a 9-8 edge in the season series. The Sox must win tonight’s series finale to even the series with the Rays in the event the teams tie for the division title. Head-to-head play is the first tie-breaker, with divisional record next in line.

The Sox had chances of their own, but couldn’t convert on their opportunities. In the eighth, Jacoby Ellsbury reached on his second infield hit of the night, but was thrown out stealing by Navarro.

In the ninth, Mike Lowell singled and Mark Kotsay walked, but Warwick’s Dan Wheeler came on to fan Jed Lowrie with the potential go-ahead run in scoring position.

The only run of the night for the Sox came in the sixth when a single by Ellsbury and an error by Evan Longoria on a grounder from Dustin Pedroia gave the Sox two on and none out.

David Ortiz moved the runners over with a grounder to right side and Kevin Youkilis hit a sacrifice fly to left to plate Ellsbury. The Sox didn’t get another baserunner past second all night.

If there was any consolation for the Sox, it came from Beckett’s strong performance. Since returning from the disabled list, he’s pitched 19 innings over three starts and allowed only 13 hits and two earned runs. In that span, he walked three and struck out 21.

“From his first start back [from the DL],” said pitching coach John Farrell, “he’s stayed within his delivery, hasn’t tried to overthrow and his curveball has been outstanding. He’s pitching as well as any time this year and probably as well as he did last year.

“From inning to inning, he’s been very consistent. He certainly pitched well enough to win on many nights.”

“I thought Beckett was tremendous,” agreed Francona.

But Tampa starter Andy Sonnanstine (one run over six innings) was almost as good.

“It’s big, especially facing a guy like Beckett,” said Sonnanstine. “He’s one of the better pitchers in the league, so I know I had to be on.”

smcadam@projo.com