Harper Begins Rehab Assignment for Nats Washington Nationals outfielder Bryce Harper started in left field and batted second as he began his minor league rehab assignment with Class-A Potomac on Tuesday night. Harper has been on the disabled list since June 2 with bursitis in his left knee and last appeared for the Nationals on May 26. Harper took pre-game warmups with a brace on his left knee and was wearing No. 32 as opposed to his regular No. 34 with the Nationals. Entering Monday night, last year's National League Rookie of the Year, had missed 25 straight games and 31 of the Nationals first 75 games this season. After having the best record in the majors last season at 98-64, the Nationals have struggled without Harper and are 37-38. Manager Davey Johnson, speaking before Washington's game against Arizona, said Harper likely won't rejoin the Nationals this weekend when they travel to New York. "I doubt if he'll be able to make it that quick," Johnson said, pointing to a series starting next Monday in Washington against Milwaukee for Harper's likely return. He'll probably do three or four innings tonight, and then, if there's no problem, gradually up it. Outfielder Jayson Werth, who left Sunday's game with a strained left groin, was in the Nationals' starting lineup against Arizona. The Nationals also placed pitcher Dan Haren on the 15-day disabled list, retroactive to Sunday, with right shoulder inflammation. They also recalled first baseman-outfielder Tyler Moore from Triple-A Syracuse. Haren underwent an MRI exam Monday, which he said revealed no structural damage, and he received a cortisone shot. "There's nothing surprising definitely," Haren said. Obviously, there was a little bit of inflammation and stuff in there. I don't know if that's normal wear and tear, or maybe a little bit more than normal. I got a shot, which is the best way to take out all the stiffness and any inflammation that's in there. The 32-year-old right-hander said he could begin throwing again as early as Wednesday. Signed to one-year, $13 million contract in the offseason, Haren is 4-9 with a 6.15 ERA in 15 starts. On Saturday, he lasted just 3 1/3 innings, surrendering six runs on seven hits in a 7-1 loss to Colorado. Moore is batting .158 with five doubles, two home runs, 13 RBIs, and seven runs scored in 38 games this season with the Nationals.