Hairston could help Lopez and the Brewers cover second base while Weeks sits 2-6 weeks with a severely sprained left ankle. But Hairston will probably be more active in center field, where he will serve as the right-handed half of a platoon in place of Carlos Gomez, who had surgery last week for a fractured collarbone. Had Hairston been able to make it to the park on time on Saturday, he probably would have started in center field against Astros left-hander J.A. Happ.
"Versatility comes into play, with as many injuries as there are in the game today," Melvin said. "He can play all over."
The Brewers moved left-hander Mitch Stetter from the 15-day to the 60-day disabled list to make room for Hairston. Stetter will undergo season-ending left hip surgery on Tuesday.
To clear a spot on the 25-man roster, the Brewers designated outfielder Brett Carroll for assignment.
Hairston played in 75 games for the Nationals this season -- 44 at third base while starter Ryan Zimmerman nursed a rib-cage injury, 22 in left field, nine in center field, three at second base and one at shortstop. Lifetime, he's played second base more than any other position -- 592 games of 1,223 total.
"I'm a player that plays everywhere, and [the Nationals] had been losing the last two weeks, so you knew something could happen," said Hairston. "The last time I got traded, we won a World Series. Hopefully it can happen again."
Hairston was traded from the Reds to the eventual World Champion Yankees on July 31, 2009.
He may have been a good omen on Saturday. Hairston, who flew into Chicago's O'Hare Airport and was driven north to Milwaukee, stepped into his new clubhouse just as the Brewers' Corey Hart hit a leadoff home run to spark a 6-2 win over the Astros.
This season, Hairston is hitting .268 with a .342 on-base percentage and four home runs. He is a career .258 hitter, but was a pain for the Brewers at Miller Park, batting .317 there in 63 at-bats.
Hairston will cost the Brewers about $675,000 over the final two months of the season, and will be a free agent at season's end.
Melvin's July trades for reliever Francisco Rodriguez and infielders Lopez and Hairston give the Brewers roster flexibility. Manger Ron Roenicke can draw from two relatively stretched-out -- if seldom-used -- relievers in Marco Estrada and Tim Dillard, two closers in John Axford and Rodriguez, two left-handed bench bats in Craig Counsell and Mark Kotsay and two right-handed bench bats in Hairston and Josh Wilson. Kotsay has appeared at all three outfield positions, and Counsell, Hairston and Wilson have experience all over the infield. Hairston and Wilson can play the outfield, too.
"[The team] has changed," manager Ron Roenicke said. "With Rickie going down, which is a big blow, I think we've done pretty good to not fill his spot, but at least make us versatile enough that we have guys who can move around. Hopefully somebody gets hot and picks up that slack for Rickie."
In trading Komatsu, the Brewers were dealing from a position of relative strength. Minor League outfielders Caleb Gindl, Komatsu and Logan Schafer all must be added to the 40-man roster in the coming offseason to protect them from the Rule 5 Draft.
Komatsu was batting .293 with a .393 on-base percentage at Double-A Huntsville.
"We like Eric, but we have Schafer and Gindl ahead of him, obviously, because they are at Triple-A," Melvin said. "Schafer and Gindl have the ability to play center field, too. Erik is a good hitter -- he has a compact swing -- and we hate to give him up. But there's a little bit of depth for us with having [Ryan] Braun and [Corey] Hart, still having Gomez and having Nyjer Morgan with us next year. We probably dealt from depth."
The non-waiver Trade Deadline is 3 p.m. CT on Sunday, but Roenicke spoke in the past tense on Saturday afternoon of the Brewers' deadline talk. Melvin remains on the lookout for an effective left-handed reliever, but has not been inspired by the list -- and the asking prices -- of available arms.
If the Brewers are done, Melvin will have made three moves without subtracting any Major League talent. The Mets will choose by Sept. 1 from a list of five mid-level prospects to complete the Rodriguez trade. Lopez cost the Brewers only cash, and Hairston cost a somewhat blocked outfielder in Komatsu.
"I like what we have," Roenicke said. "I think you also have to look at what we gave up to get these guys, and [Melvin's team] did a great job. You hate to give away too many prospects."