For Tim Lincecum, it has been a season of one step forward and two steps back.

The San Francisco ace looks to rebound from yet another disappointing outing this afternoon as the Giants conclude a three-game series against A.J. Burnett and the Pittsburgh Pirates.

Lincecum has two National League Cy Young Awards to his credit, but has hardly pitched like an ace this season. He is 3-9 with a 6.08 earned run average in 17 starts, with San Francisco just 4-13 in those games.

The right-hander looked to have turned a corner when he halted a 10-start winless streak by throwing seven shutout innings to beat the Dodgers on June 27. Lincecum also fanned eight, but came back on Tuesday in Washington and yielded a career-high eight runs -- seven earned -- on nine hits and two walks over 3 1/3 innings of a loss.

The Giants are hoping it was the heat -- which came in at 94 degrees -- that bothered Lincecum and that it wasn't just another poor outing.

"It just got the better of me a little bit," Linceum said. "They made me work and made me pay for it."

The 28-year-old has struggled to a 1-5 mark and 8.45 ERA in nine road games this season. In four lifetime meetings with the Pirates, Lincecum is 1-1 with a 3.10 ERA.

Burnett, meanwhile, has looked like an ace for most of the season, going 9-2 with a 3.74 ERA in 14 starts.

The right-hander was bidding for a ninth straight winning start on Tuesday against Houston, but instead did not factor into an 8-7 win after giving up six runs on 12 hits over five innings. It was the first time he did not get a win since a no-decision on May 13, though Burnett still hasn't lost since May 2.

Furthermore, the Pirates have won all 11 of Burnett's starts since that setback.

The first-year Pirate has gone 5-0 with a 2.01 ERA in eight starts at home this season. In seven career meetings with the Giants, the 35-year-old is 5-2 with a 1.84 ERA.

Burnett looks to pitch Pittsburgh to a series win today after the club took Saturday's meeting 3-1. James McDonald tossed seven innings of one-run ball, striking out 10 while scattering four hits without a walk.

"Getting ahead of guys and being aggressive was my game plan," McDonald said. "Don't be afraid of (anybody) and go right after them. I had good fastball command today and got ahead of a lot of guys. I put them away when I had to."

Neil Walker doubled twice and drove in a run while Michael McKenery and Pedro Alvarez had an RBI apiece for the Pirates, winners in nine of their last 11 and holders of one-game lead over the Reds for first place in the National League Central.

Ryan Theriot had a pair of hits and drove in the lone run for San Francisco, which has dropped six of its last eight. Ryan Vogelsong was pegged with the loss after giving up three runs on eight hits while fanning five over seven innings.

"Obviously (McDonald) is having a good season," Vogelsong said. "Throwing the ball well so going in you know it is going to be a tough game. He pitched a little bit better than me today."

The Giants took two of three from the Pirates earlier in the year and have won 14 of their last 21 against them.