DENVER -- Bryce Harper is getting daily treatment on his back, which he tweaked while diving for a ball June 7 against the Mets. "I've seen him with all kinds of contraptions [on his back], but I think right now it's for prevention," Nationals manager Davey Johnson said. Harper has started all but one game since being called up on April 28. He's drawn attention for, among other things, his aggressive style on the basepaths and in the outfield, playing at times like his hair is on fire.

"The one thing I never try to do is turn down somebody's aggressiveness, it's hard enough to try to turn it up," Johnson said. "I like to see everybody play all-out. With experience, [Harper] will feel that warning track and realizes he doesn't have to be going 100 miles per hour."

In his previous 10 games before starting Monday against the Rockies, Harper had a .205 batting average (8-for-39) with 11 strikeouts, one RBI and no homers.

DeRosa activated; Nady goes on DL

DENVER -- After missing 50 games with a left oblique strain, Mark DeRosa was reinstated by the Nationals on Monday. To make room, outfielder Xavier Nady was placed on the 15-day disabled list with tendinitis in his right wrist, retroactive to June 24.

DeRosa went on the 15-day disabled list April 28 after just 13 games. In that time, he was 3-for-37 from the plate (.081) with two RBIs and appeared defensively at the corner spots in the infield, as well as some outfield.

DeRosa also mourned the death of his father, Jack, who died June 12 after a prolonged battle with cancer.

"It feels good to be back," he said. "I've got to get back in the flow of playing everyday, it's been a whirlwind the last seven weeks."

At 37, DeRosa realizes he's no longer the same guy that played 149 games in consecutive seasons in 2007 and '08, when he hit .293 and .285, respectively. But he's been a part of 10 separate postseason clubs, so even if he's not starting every day, DeRosa can still play the role of elder clubhouse statesman.

"I think that was the biggest reason I was brought in here, to be honest with you -- get some timely hits off the bench, give some guys a breather, help some of the younger guys develop as players," DeRosa said. "I get a big kick out of watching guys like Danny [Espinosa], Ian [Desmond] come into their own. If I can be a sounding board for them, then I want to be it, because there were guys before me whose brain I picked."

Nady was hitting .157 with six RBIs and three homers in 40 games. Washington manger Davey Johnson called the move a "no-brainer."

"Xavier has been having treatment on and off for a month, maybe since the start of the season," Johnson said. "He's got swelling in his right wrist, a shot to the area could heal it but it could only get worse by him playing. It made sense to get everybody healthy."

Moore could see more time in lineup

DENVER -- The Rockies will trot out at least three left-handed pitchers in a four-game series against the Nationals, which makes for a good reason to keep hot-hitting Tyler Moore in the lineup.

In his rookie season, Moore has seen twice as many at-bats against lefties than he has against righties. His best game, however, came against right-handed pitcher Kyle Drabek in Toronto, when Moore notched three hits -- two of them homers -- to finish with 10 total bases.

"His performance has not gone unnoticed by the managerial staff," Nationals manager Davey Johnson said.

Moore was called up on April 29, then sent back on May 28. In that span, he had three hits in 19 at-bats (.158).

"He wasn't playing," Johnson said. "The worst thing you can do when a player comes up to the bigs is sit them. When he came up the second time [June 7], he was more aggressive."

Moore is hitting .375 his last 10 games. He started in left field Monday against the Rockies, and it's a good bet he'll see extensive playing time in the four-game series.

Jeff Francis, who started on Monday, is left-handed, as are Christian Friedrich and Josh Outman, the projected Tuesday and Wednesday starters. Also, the Rockies optioned right-handed starter Alex White -- Thursday's probable starter -- to Triple-A Colorado Springs on Monday. His replacement could be southpaw Drew Pomeranz

Worth noting

• Henry Rodriguez, placed on the 15-day disabled list on June 7, will likely finish his rehab assignment at Double-A Harrisburg, as the Nationals want the right-handed pitcher to be closer to Washington D.C..

Rodriguez, nursing a strained right index finger, pitched one inning of no-hit ball for Triple-A Syracuse on Sunday night.

"I think he's close to being ready," Johnson said. "We're not concerned about his [health]. We want to see him go back-to-back. He pitched last night and threw the ball exceptionally well."

• Stephen Strasburg made his first career start at Coors Field on Monday. In one other game pitched at high altitude, Strasburg gave up four earned runs in five innings at Atlanta's Turner Field (1,050 feet above sea-level).

"He doesn't like to get hit no matter what ballpark he's in, whether it's Fenway or any of the other hitting parks," Johnson said.

• The Rockies have swept the Nationals six times since the 2005 season. Among National League teams, the Nats' lowest win percentage comes against the Rockies (.327).