Jon Lester goes after a third straight win on Friday when the Boston Red Sox open a four-game series with the Kansas City Royals at Fenway Park.

Lester has endured a miserable season, but has started to turn it around, allowing just one run in each of his last two starts. He beat the New York Yankees on Saturday, holding them to a run and five hits in seven innings to run his record to 7-10, while lowering his ERA to a still lofty 5.03.

"It's always gratifying to see the fruits of your labor, for lack of a better term. It's been a grinding season," Lester said after the game. "I said back a month or so again, I'm not giving up. I'll keep working hard and things will turn. The past handful of starts, I feel like they have."

Lester lost to the Royals earlier in the year, but is 5-2 lifetime against them with a 1.35 ERA in eight starts.

The lefty could get an added boost as well with the expected return of designated hitter David Ortiz, who's been sidelined since suffering a strained Achilles on July 16. He was hitting .316 with 23 homers and 58 RBIs at the time of his injury.

"It looked like David got through everything perfectly (Thursday)," manager Red Sox Bobby Valentine said. "If he gets through (without problems), we're planning on hopefully activating him (Friday)."

The Red Sox could have used Ortiz this week when they were swept by the Los Angeles Angels of Anaheim, culminating with a wild 14-13 loss in 10 innings on Thursday that saw them blow an early six-run lead.

Boston has now lost 15 of its last 21.

"We need to try and find a way to win these," said second baseman Dustin Pedroia, who drove in five runs in the loss. "We are playing hard, but we need to find a way to be one run better."

Kansas City, meanwhile, has been playing as well as any team in the league with 13 wins in its last 21 games, despite losing two of three to the red-hot Tampa Bay Rays after a 5-3 setback on Wednesday.

Getting the call on Friday for the Royals will be lefty Bruce Chen, who is 9-10 with a 5.45 ERA. Chen won for the second time in three starts on Saturday against the Chicago White Sox, as he allowed two runs and five hits in six innings.

"He's doing fine, he made good adjustments. He's doing a great job with it and the results have shown that," Royals manager Ned Yost said. "He's pitched great his last three or four times out, I thought.

"He was just getting to where his sole focus was just to pinpoint-command the ball instead of a little more attack, a little more focused on changing speeds and pitching."

Another win for Chen tonight would mark three straight seasons with at least 10 victories, making him the first Royals lefty to accomplish that since Charlie Leibrandt in 1988.

Chen beat the Red Sox the last time he faced them and is 4-6 in 17 games (10 starts) against them with a 5.76 ERA.

Kansas City took two of three from the Red Sox earlier in the year.