Even though Jair Jurrjens was 3-0 with a 2.13 ERA in his first four starts after returning from Triple-A, and Ben Sheets pitched six scoreless innings Sunday to win his first major league start in two years, the Braves have continued to explore a possible trade for a front-line starting pitcher.

Tuesday night was a reminder why.

Jurrjens was charged with eight runs and eight hits in 3 1/3 innings as the Braves' seven-game winning streak ended with the thud of a 9-0 loss to the San Francisco Giants in a series opener at Turner Field.

Leesburg native Buster Posey had three hits and five RBIs in the first four innings, including a three-run double off rookie reliever Luis Avilan to cap a six-run fourth inning that gave the Giants an 8-0 lead.

Barry Zito (8-6) held the Braves to three hits in seven innings and improved to 4-0 with a 1.63 ERA in five starts at Turner Field. The left-hander is 4-1 in six overall starts against Atlanta.

The Braves scored six or more runs five times during their winning streak, but against Zito one runner advanced past first base until Freddie Freeman's two-out double in the seventh inning. Martin Prado's fourth-inning single was their first hit.

Jurrjens (3-3) allowed only six earned runs in 25 1/3 innings in his first four starts since returning from a two-month minor league stint. But he reverted to something closer to his early-season form, when he had a 9.37 ERA in four April starts before being demoted to Triple-A.

Although the Braves had a 3.00 ERA during the seven-game winning streak, they've given up 22 earned runs in 36 innings over their past four. Sheets' outing Sunday was their only quality start in that four-game stretch. In the other three, starters Tim Hudson, Tommy Hanson and Jurrjens allowed 18 earned runs in 12 2/3 innings.

The eight runs were Jurrjens' season-high, and the 3 1/3 innings was his second-shortest outing. He lasted three innings (five runs, nine hits) in an April 23 loss against the Dodgers in Los Angeles, and was optioned to Gwinnett an hour later.

He'd had encouraging performances since returning, including 7 2/3 innings of three-hit ball at Boston in his first game back. But Jurrjens has only 11 strikeouts in 28 2/3 innings over five starts and allowed 23 hits in 15 1/3 innings over his past three.

He was victimized early by sketchy defense and an umpire's close call. But by the fourth inning the Giants teed off on Jurrjens, whose fastball velocity was down a tick or two from previous starts, in the 86-89 mph range.

The last three runs on Jurrjens' ledger were driven in by Posey against Avilan, after the former Lee County High star drove in a pair against Jurrjens with a double in the first inning and single in the third. Posey was the 2010 NL Rookie of the Year over Atlanta's Jason Heyward, who played for Henry County High when it defeated Posey and Lee County in a 2005 Georgia state championship series.

Posey was the first batter faced by Avilan, a left-hander who was brought in after Jurrjens gave up five hits and a walk to the first seven batters of the inning. Braves manager Fredi Gonzalez brought in Avilan, though Posey had a .367 average and 1.022 on-base-plus-slugging percentage against lefties before his bases-clearing double off the rookie.