When the Giants and Padres wrapped up a three-game series on June 19, San Francisco was in second place by 1 1/2 games in a hotly contested National League West, while San Diego was three games back.
Everything since has been a struggle, as both teams limp into a four-game series in San Diego to close out the season's first half.
The Giants took two of three from the Padres in their most recent meeting, but that was the last time San Francisco won a series. Including the recent sweep at the hands of the Mets, the Giants are 3-16 in their last 19 games, having lost eight of the last nine to fall a season-high seven games back in the division.
Meanwhile, the Padres snapped a 10-game losing streak on Tuesday but lost again Wednesday night and sit even with the Giants -- 10 games below .500.
"It's not exaggerated. When you're going through a streak, it wears on you mentally as much as physically," San Francisco manager Bruce Bochy said. "It's been a daily issue. We're playing and there's a lot of faith we'll get out of this."
Seemingly everything that can go wrong has for the Giants, who saw Matt Cain fail to make it out of the first inning for the first time in 254 career starts on Wednesday. Citing a play in Tuesday's game when Gregor Blanco hit a hard liner that could have scored a run but was instead caught and turned into a double play, Bochy said luck hasn't been on the Giants' side and some of his guys are pressing to make things happen.
"I couldn't be prouder of how the guys have handled [the struggles]," Bochy said. "They want to come out of this. Sometimes it takes a little longer than you like."
On Thursday, the Giants will turn to left-hander Madison Bumgarner, who pitched in San Francisco's only win in the last nine games. The Padres will look to right-hander Jason Marquis as they try to put a winning streak together heading into the All-Star break.
Padres: Marquis takes fifth attempt at 10th win
Jason Marquis has been sitting on nine wins since he beat the D-backs on June 15. When he takes the hill for the Padres on Thursday, he'll look for win No. 10 against a team he's already defeated once this season.
As part of a three-game sweep over the Giants in April, Marquis surrendered two runs and scattered six hits and four walks across 6 2/3 innings against San Francisco for his second win of the season. Since collecting his ninth win, the 34-year-old right-hander is 0-2 with a 4.37 ERA in four starts.
Most recently, Marquis gave up three runs on eight hits and three walks in a no-decision against the Nationals. He was line for the win after his six innings of work before the bullpen squandered a late lead.
• Padres manager Bud Black announced Wednesday that Sean O'Sullivan will start Friday's game. O'Sullivan, who went to Valhalla High School in El Cajon, is 7-4 with a 3.88 ERA this season for Triple-A Tucson.
Giants: Bumgarner seeks third straight win
Although the Giants haven't been able to win back-to-back games since June 18-19 against the Padres, Madison Bumgarner will look for his third straight victory on Thursday.
Bumgarner delivered one of his best outings of the season on Saturday, limiting the Dodgers to two runs and three hits in seven innings in a 4-2 win. The 23-year-old also fanned nine, falling one strikeout short of his fourth double-digit strikeout game of the season.
Bumgarner has won five of his last six decisions, including a win over the Padres on June 19, when he went seven innings and surrendered two runs on three hits and four walks.
• The Giants could get a boost this weekend from reliever Santiago Casilla, who said on Wednesday that he expects to come off the disabled list on Thursday and travel with the team to San Diego. Casilla has been on the DL since May after having surgery to remove a cyst from his right knee.
Casilla built a 1.89 ERA in 21 appearances before hitting the DL, and San Francisco has struggled without its go-to setup man.
• Hunter Pence will need some help if he wants to make his way onto the NL All-Star team. One of five players chosen for the league's Final Vote, Pence ranked third behind the Braves' Freddie Freeman and the Dodgers' Yasiel Puig as of the third update on Wednesday morning. Voting ends at 1 p.m. PT on Thursday.
• Thursday marks the beginning of the fourth series of the season between the Padres and Giants, with San Francisco going 5-4 in the first nine games. The Padres swept the previous series in San Diego.
• The Giants enter Thursday with 21 runs scored in July, the fewest for any team in the Majors.
Jeremy Warnemuende is an associate reporter for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.