PHOENIX -- Brandon Webb was expecting to throw long toss again on Monday before his D-backs played the Cardinals at Chase Field. The injured right-hander was placed on the 60-day disabled list on Sunday, meaning that he's not available to be activated until May 25 at the earliest.

"I'm just trying to get through it," said Webb, who hasn't thrown in a game in more than a year and is still recovering from surgery last August to clean out his right shoulder.

"I'm up to about 110 feet again and maybe in about five days I'll try pitching on flat ground. So far, I'm feeling good. Just a few steps forward, a few back. There's nothing you can do about it."

Webb had thrown a number of bullpens early in Spring Training, but hasn't worked off a mound since his arm felt lifeless during a session in Tucson on March 4. There's no timetable for his return.

D-backs place Jackson on 15-day DL

PHOENIX -- A day after left fielder Conor Jackson strained his right hamstring making a catch in San Diego, the D-backs placed him on the 15-day disabled list Monday hours before playing the Cardinals at Chase Field.

Jackson was replaced on the 25-man roster by right-handed reliever Esmerling Vasquez, who was recalled from Triple-A Reno. The move gives Arizona 13 pitchers, eight in the bullpen.

"We're going to go with the extra pitcher at least until when we feel better about where the pitching is," said D-backs manager A.J. Hinch, whose club has lost four in a row, three of them because of collapses by the bullpen.

Jackson, batting .267 with no home runs and two RBIs in 11 games, underwent an MRI on Monday, which revealed no significant damage.

"[The doctors] are not overly concerned that he would miss more than a week, a week and a half," Hinch said. "But we're not afforded the luxury of playing short for that long either from the pitching side or the position-player end of things. He'll probably be ready to return before the time period is over."

Considering the fact that he missed most of the 2009 season battling valley fever, Jackson called the latest turn of events "frustrating."

"I missed most of last year and 12 days in I'm already on the 15-day DL. So this is pretty disappointing," Jackson said. "Im not going to sit here and mope on it. I'm going to get better, get back out there and try to help the team. I'm going to rehab my butt off for the first 10 days and for four or five days after that do some work down in Tucson in extended [spring training]. Then I'll rejoin the team in Houston [on May 3]. At least that's the plan."

Jackson injured himself lunging awkwardly to make a catch on Sunday to end the Padres' five-run seventh inning in a 5-3 loss.

Jackson is already the second regular the D-backs have lost this season. Catcher Miguel Montero injured his right knee running out a grounder on April 10 and had to have surgery to repair a torn meniscus.

LaRoche returns to D-backs lineup

PHOENIX -- After missing four consecutive games with a strain in his upper right quadriceps, Adam LaRoche was back in the D-backs lineup Monday for their homestand opener against the Cardinals at Chase Field.

LaRoche was back in his accustomed spots at first base and batting fourth.

"It wasn't bothering me hitting at all, but I just couldn't full out run," he said prior to batting practice. "It could be worse considering other guys around here."

LaRoche said he sustained the injury last Wednesday against the Dodgers in Los Angeles and played through it all game.

"I started feeling it early in the game and I think I finished it off running out a double," said LaRoche, who's batting .258 with no homers and five RBIs in nine games. "After that I stayed in, but that just didn't help at all."