The Rays’ Jason Bartlett steals second base ahead of the tag by Red Sox shortstop Julio Lugo during the eighth inning of yesterday’s series finale at Tropicana Field.

AP / Mike Carlson

ST. PETERSBURG, Fla. — The bats must be sick and tired, too.

The formerly potent Red Sox offense has gone astray, and Boston now has lost five straight games, including a 3-0 setback to the Tampa Bay Rays yesterday at Tropicana Field. During this horrid stretch, which included 20 straight games between off-days, the Red Sox have been depleted by the flu and injuries.

Boston has been hoping for some relief from its current struggles and it found it in the way of starting pitching in the last two games. The problem, however, was those starters didn’t get any help offensively.

Red Sox pitcher Josh Beckett was back in the mix yesterday after missing his last start with a stiff neck. The right-hander was solid, going seven innings and allowing only two runs (one earned) on four hits with a career-high 13 strikeouts — only to suffer the loss. The offense had only two hits.

His effort came on the heels of Clay Buchholz’s three-hit performance during Saturday’s 2-1 loss, in which the Red Sox generated only five hits. Boston simply hasn’t been able to come up with the timely hits.

“Our offense carries a lot of the load around here,” Beckett said. “It’s time for us [pitchers] to start stepping in that direction or maybe it’s our turn to start carrying our load.”

Speaking of solid pitching performances, the Rays’ James Shields pitched a complete-game shutout, the first of his career, and allowed only two hits — Dustin Pedroia and Julio Lugo each had a single — with one walk and seven strikeouts. The right-hander was in control from start to finish. While the Red Sox were blaming the loss on their lack of offense, they weren’t about to take anything away from Shields.

“It’s not the first time that kid has pitched that kind of game,” said Beckett. “It won’t be the last time he ever out-pitches anybody, either. He deserves a lot of the credit for what he did.”

Despite the weekend sweep here and the current losing skid, Red Sox captain Jason Varitek was able to find something positive from the weekend losses — the starting pitching.

“It was very well needed for our bullpen to get those outings,” he said. “Things need to match up to win games. Obviously, they pitched real well, but we didn’t swing the bats well, either.”

With the way Beckett was pitching, along with the struggles of Boston’s offense, Tampa needed only three runs to put this one away.

Beckett retired seven of the first eight batters he faced until the Rays’ Jason Bartlett got Tampa’s second hit of the game, a one-out single in the third inning. The speedy Bartlett took his lead at first. When Beckett attempted a pick-off, the ball was thrown to the outside of the runner, out of Kevin Youkilis’ reach as it rolled along the wall in foul territory.

Bartlett reached third on the miscue, then scored on a throwing error by right fielder J.D. Drew on the same play.

“I just flew open, trying to be too quick,” said Beckett, referring to the attempted pick-off. “I’m not that athletic.”

Beckett said he made another mistake when he allowed a solo home run to the Rays’ Evan Longoria to lead off the seventh inning that gave Tampa a 2-0 lead.

“I feel good,” he said. “I’m just not happy with the results today. I basically lost the game for us. I threw the ball away and then hung a curveball to Longoria.”

Tampa pushed a run across in the eighth inning off reliever Manny Delcarmen for a 3-0 final.

Boston left here immediately after the game knowing that it had lost two consecutive games in which its starters were nearly unhittable.

“It’s tough,” Pedroia said. “We didn’t swing the bats very well this whole series, but that’s how it goes. We swung the bats great for three weeks in a row. Then we hit a stretch where we got great starting pitching and didn’t hit. That’s how it goes. We just need to put both together and we’ll be fine.”

“Josh threw well,” said Varitek. “The key, obviously, [is] we didn’t get it done offensively.”

Before the final out was made yesterday, there was a rare sighting at Tropicana Field, which can be considered Fenway Park South due to all the Red Sox fans in attendance. Of the 32,363 in attendance, those who are Rays fans were holding brooms for the sweep of the defending world champions.

jmcdonal@projo.com