Giants manager Bruce Bochy has expressed recent concern about the back end of his rotation. Hopefully the bullpen isn't becoming an issue as well.

One night after All-Star closer Brian Wilson failed to lock down a series- opening win, San Francisco turns to the struggling Jonathan Sanchez as it tries to even its four-game set with the Atlanta Braves at Turner Field.

Wilson was called upon to protect a two-run lead in the ninth inning, but gave up a one-out single to Martin Prado before walking Brian McCann, who had homered earlier in the game, to load the bases.

After striking out Dan Uggla, rookie Freddie Freeman worked a full count off San Francisco's bearded closer before bouncing a two-run single up the middle to secure a walk-off victory for Atlanta.

A Rookie of the Year candidate, Freeman is hitting .296 this season with 16 homers and 60 RBI.

"So far, yes," Freeman said when asked if his game-ending hit was the biggest thrill of his young career, "especially when you're in a playoff race and playing a team right behind you in the wild card."

Atlanta avoided a third straight loss by beating San Francisco for the sixth straight time in the regular season, advancing its lead over the franchise in the wild card race to five games.

Wilson, meanwhile, suffered his fourth defeat of the season and fifth blown save, matching his total from a year ago in 15 fewer games.

"They won the battle," said Wilson, who has a 3.19 earned run average on the season and was unavailable on Sunday due to back spasms.

The Giants, who were trying to win three straight for the first time since July 17-19, instead lost for the 12th time in 17 games and fell 2 1/2 contests back of the idle Diamondbacks for first place in the National League West.

Bochy will now hope that Sanchez can win for the first time in seven starts as the left-hander is 0-4 with a 6.14 ERA over his winless streak. He has allowed nine earned runs in back-to-back losses, giving up four of those, and five runs total, on four hits and four walks in a loss to the Pirates on Wednesday. He failed to pitch out of the fifth inning for a fourth straight outing.

"It has me a little concerned," Bochy said of the instability at the fifth- starter spot. "We need that guy to help us win a ballgame, too. We haven't had a good start there in I don't know how many times now."

Sanchez, 28, is 4-7 with a 4.29 ERA in 18 starts this year, including a no- decision on April 24 against the Braves when he allowed two runs over five innings. He is 1-3 lifetime when facing Atlanta, posting a 5.63 ERA in eight games.

The Giants are likely to be without Pablo Sandoval tonight after he fouled a ball off his right foot in the first inning on Monday. X-rays on the foot were negative.

San Francisco was already without Carlos Beltran for a seventh straight game because of a right wrist injury and the outfielder may miss this entire series and end up on the disabled list.

The Braves, meanwhile, should have Chipper Jones back in the starting lineup after the third baseman rested his left knee in Monday's opener.

That should be good news for young right-hander Randall Delgado, who will replace an injured Tommy Hanson for the second time this year as he goes for the Braves tonight.

Delgado made his major league debut back on June 17 when Hanson was out, allowing four runs -- three earned -- on seven hits and two walks over four innings of a loss to Texas. The 21-year-old will be summoned from Triple-A Gwinnett to once again fill in for Hanson, who is on the disabled list because of right shoulder tendinitis.

In 23 minor league starts this season, including two since a recent promotion to Gwinnett, Delgado is 7-5 with a 3.45 ERA.