Another Los Angeles Dodgers starting pitcher has issues. This time it's Josh Beckett.He remained winless this season in a 6-2 loss to the Washington Nationals on Monday night, leaving after three innings when he tweaked his groin covering first base on a grounder by Adam LaRoche.The Dodgers, who ended an eight-game skid over the weekend, have since lost two in a row. Their pitching ranks have already been disrupted with Zack Greinke, Chris Capuano, Chad Billingsley, Ted Lilly, and Stephen Fife putting in time on the disabled list barely 1 1/2 months into the season.Now Beckett has "had some stuff going on," manager Don Mattingly said without offering specifics.Besides the groin tweak, Mattingly said, "Part of the other stuff that's been going on is part of the reason I got him out of there."It was Beckett's shortest outing of the season after he hurt himself in the third."I threw about 10 pitches after that," he said. "My groin hadn't been bothering me. I've don't think I've ever had groin problems."Beckett (0-5) gave up four runs - two earned - and three hits in three innings while striking out five and walking two."The problem is that I'm just stinking. I'm in one of those ruts right now," he said. "It seems like if they hit the ball soft it's a hit, if they hit the ball solid, it's a hit. I have to figure out a way to get out of it."Beckett also declined to go into details on what his other issues are, saying, "I'm not a doctor. I don't know how they treat things here. We're day-to-day with things, trying to treat things. I'm trying to make pitches and I'm not doing a very good job right now."The Dodgers trailed 6-1 in the sixth on Skip Schumaker's RBI groundout. Matt Kemp's RBI single in the eighth drove in their other run and extended his hitting streak to 12 games.Jordan Zimmermann won his NL and major league-leading seventh game and Ryan Zimmerman drove in three runs for the Nationals after they lost Bryce Harper in a violent collision with the wall in right field.Zimmermann (7-1) allowed nine hits and two runs in 7 2-3 innings, struck out five and walked none.Harper left the game in the fifth after hitting the scoreboard wall face-first while tracking a ball hit by A.J. Ellis over his left shoulder. He never looked at the wall and when he finally turned, he was on top of it. The impact sent Harper's cap flying as he bounced off the wall and crumpled to the ground, with Ellis getting a triple.Harper rolled onto his back and eventually got up under his own power. Streaks of blood were evident on his neck as he walked off the field. There was no immediate update on his condition before the game ended.He was playing just his second game after missing two with an ingrown toenail that required surgery.The Nationals ended a five-game skid at Dodger Stadium, where they were swept last year when Harper made his major league debut.Zimmerman's RBI grounder in the first gave Washington a 1-0 lead. His RBI double added two more runs in the third, when Adam LaRoche made it 4-0 on a RBI groundout. Beckett gave up three runs on one hit in the inning.The Nationals extended their lead to 6-0 in the fifth. Zimmerman grounded into a fielder's choice to pitcher Javy Guerra, and Steve Lombardozzi scored on Guerra's throwing error. LaRoche's RBI single scored Harper, who walked.It wasn't Harper's first collision with the wall at Dodger Stadium. Last year in the second game of his career he hit the center-field wall while making a catch and hurt his back.On April 30 in Atlanta, he bruised his left side leaping toward the fence while trying to prevent a home run.Notes: Nationals RF Jayson Werth, on the 15-day DL with a strained right hamstring, will see a doctor in New York on Tuesday. He's likely to rejoin the team this weekend in San Diego. ... Dodgers RHP Zack Greinke will pitch on Wednesday; the team just isn't sure whether it will be for them or at Single-A Rancho Cucamonga. He is on the 15-day DL with a broken left clavicle. ... Dodgers 1B Adrian Gonzalez returned after getting Sunday off, and extended his hitting streak to 10 games with a single in the first. ... The Nats improved to 16-2 when scoring first this season. ... The Nats opened a 10-game trip, tying their longest of the season.