The Padres will try to put the first half of the season behind them when they take the field on Friday in St. Louis.

San Diego enters the second half having lost 18 of its last 22 games and will send Jason Marquis to the mound against his former team. Marquis recorded nine victories in his first 14 starts but has stalled there in his last five outings, and still searches for an elusive 10th win.

Marquis has issued the most walks (65) in the Majors, but the Padres aren't concerned about the free passes, especially since Marquis is 9-4 with a 3.77 ERA.

"Some of those walks, I call them 'navigating his way through a ballgame,'" said pitching coach Darren Balsley. "He's stubborn, and he doesn't actually pitch around guys. He's going to throw the ball where he thinks they can't put it in play hard."

Marquis had 12 quality starts in the first half, his most since posting 13 in all of 2011 and nine shy of his career-best 21 in 2009, his lone All-Star campaign. Friday will be Marquis' second start this season against the Cardinals, with whom he spent the 2005-06 seasons.

Starting for St. Louis is Jake Westbrook, who will be making his seventh start since coming off the disabled list in mid-June. He has looked good in his three wins, but he has also dropped three contests, including his most recent -- a 5-4 loss to the Cubs on Thursday in which he allowed three earned runs on seven hits in seven innings.

"I wasn't as sharp as I have been, but I was able to get back in the zone and make some good pitches," Westbrook said. "I felt like I battled and was able to get deep in the ballgame and give us a chance."