SAN DIEGO -- Pitcher Andrew Cashner had an MRI on Friday that confirmed that he has a strained right lat muscle.
Cashner is currently on the disabled list and receiving treatment for the injury. There's no timetable for his return, though it likely will exceed more than one month.
San Diego closer Huston Street missed 29 games with a similar strain and starting pitcher Eric Stults is currently on the disabled list with the same injury. Stults, who has missed 29 games, is scheduled to throw a simulated game on Saturday at Petco Park.
"I would suspect the same -- a month," said Padres manager Bud Black, who noted that Cashner will need at least a few Minor League rehabilitation starts before he returns.
Cashner left the game early against the D-backs on Tuesday after feeling pain while warming up for the bottom of the third inning. It was Cashner's second start since he moved into the starting rotation from the bullpen, where he was the Padres eighth-inning specialist.
Headley brushing off trade talk, wants to stay put
SAN DIEGO -- There has been a lot of buzz in the industry recently about Padres third baseman Chase Headley, especially as the non-waiver trade deadline of July 31 creeps closer each day.
Headley has noticed reports that have him as a desirable target for teams looking for a third baseman: one who hits much better away from spacious Petco Park, is durable, a switch-hitter and under team control for two more seasons.
"It's a different experience," Headley said Friday when asked about hearing his name mentioned so frequently. "You understand that's part of the business and very few players in this day and age stay with the same team for their entire career, much less five years.
"But I'm just trying to ignore it because I have no control over it. It will be nice when the month is over so I don't have to hear about it anymore."
Don't get the impression that the Padres are shopping Headley. General manager Josh Byrnes said that he's not seeking to move Headley, though he's certainly listening to offers, as he is with other players on his roster.
The thinking internally is that it will take a lot to part with Headley, who went into Friday's game with the Reds hitting .272 with eight home runs, 42 RBIs and a .374 on-base percentage. His OPS on the road (.811) is considerably better than it is at home (.667) for his career.
For his part, Headley -- who was drafted by the Padres in 2002 and made his Major League debut in 2007 -- doesn't want to go anywhere.
"San Diego is the only organization I've ever been in. I'd like to win some more games but I think we're on the right path," he said. "We have some guys coming up who are making good contributions. The talent is close to being where it needs to be.
"If it were my choice, I would love to be here."
Marquis to start Sunday on three days' rest
SAN DIEGO -- Padres manager Bud Black announced Friday that Jason Marquis will start Sunday's series finale with the Reds on three days' rest.
Black said he chose Marquis over the righty Ross Ohlendorf, who will assume his role as long reliever until the All-Star break. Ohlendorf was available Friday and could be a fit to relive Marquis on Sunday if needed.
Marquis' last outing came July 4 in Arizona, a no-decision in which he gave up four runs on eight hits in 6 1/3 innings. In six career starts on three days' rest, the 33-year-old is 1-2 with a 3.93 ERA.
Since being called up to San Diego on June 7, Marquis has a 3.49 ERA and a 1-4 record in six starts. He has struck out 39 batters in 38 2/3 innings of work, including a 10-strikeout showing in a June 18 loss to Texas.
Black has not yet announced whether or not he plans to reset his starting corps for the second half, which begins July 13 with a three-game set against the Dodgers in Los Angeles.
Black said he will most likely announce his pitching plans for that series on Sunday.
Pitcher Eric Stults, on the disabled list since June 4 with a strained left lat muscle, will throw between 30-40 pitches Saturday in a simulated game at Petco Park. There's a chance Stults could begin a rehab stint on July 12 with Triple-A Tucson.
The Padres have had pinch-hit home runs in each of their past three games, tying a Major League record set by the 1984 Dodgers and the Marlins this season. On top of that, the Marlins streak is current -- which means both the Padres and Marlins have had pinch-hit home runs in each of the last three days.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. Chelsea Janes is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.