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Coming off a rough series in Milwaukee, the San Francisco Giants return to AT&T Park on Friday to begin a three-game set with the division-rival San Diego Padres.

The Giants suffered a three-game sweep at Milwaukee this week, as the pitching staff watched 21 runs cross the plate. On Thursday, they trailed 7-0 after three innings and went on to lose, 7-2. San Francisco has given up three runs or more in eight different innings this season.

"You look at the early going here, it's kind of been strange, the big innings we're giving up," Giants manager Bruce Bochy said. "I think we're fortunate to be [9-7]. We've had some good comebacks, but we get down a little bit more than we care to, to be honest, where we've had to make these comebacks. We've had a tough go here staying away from the crooked number. That's what beats you in a lot of games."

San Diego was idle on Thursday. The Padres remain at the bottom of the NL West standings, although they began this road trip with a three-game sweep over Los Angeles at Dodger Stadium this week. The Padres won Wednesday's finale, 7-2, and they out-scored the Dodgers for the series, 22-7.

Third baseman Chase Headley, the National League leader with 115 RBI last year, made his season debut for San Diego on Wednesday and went 1-for-4. Headley broke the tip of his left thumb in spring training.

San Diego will turn to right-hander Edinson Volquez, who has failed to complete four innings in two of his three starts. Volquez, the Opening Day starter, fell to 0-3 against the Rockies on Saturday, as he gave up six earned runs and issued three walks in 3 1/3 innings before getting the hook. Opponents are hitting .356 against him.

"You're going to have some rough starts, and Volquez has had his right from the start," Padres manager Bud Black said. "Let's hope he can get it straightened out. Right now, his issues stem from ball-to-strike ratio, and getting ahead in the count. When you get behind, you can get in some trouble."

Meanwhile, Giants southpaw Madison Bumgarner has enjoyed a much different start to his season. Bumgarner is 3-0 with a 1.77 ERA after three starts, and he has fanned 17 batters in 20 1/3 innings of work. The left-hander is trying to be the first NL pitcher to reach four wins, and it would also mark the first 4-0 start of his career.

The Giants have taken the season series against San Diego in each of the last two years, winning 12 of 18 meetings both times.