ST. LOUIS -- The Cardinals finally got their impact bat.

Addressing a glaring need as well as answering their manager's longstanding clarion call, the Redbirds acquired Matt Holliday from the A's in exchange for Brett Wallace and two other Minor Leaguers, Triple-A right-hander Clayton Mortensen and Double-A outfielder Shane Peterson. Holliday is the second significant acquisition by St. Louis this season, joining Mark DeRosa, and is the club's biggest in-season pickup since a 2004 trade for Larry Walker.

Oakland will send cash to St. Louis to help offset the remaining cost of Holliday's contract. Holliday, 29, can be a free agent at the end of the 2009 season. His current contract pays him $13.5 million, of which approximately $6 million is still due.

That, however, was not enough to deter the Cardinals front office, which has taken a great deal of heat in recent years for being cautious. No such criticisms can be leveled at it in 2009. The move is a clear indication of a win-now philosophy for the Cardinals, who acquired DeRosa from Cleveland in June. They are locked in a four- or five-way battle for the National League Central title, but with their second upgrade in a month, may now be considered the favorites.

"It's always difficult [to make a deal like this]," general manager John Mozeliak said. "But if you feel that you're getting a deal that you believe is fair, even though it may have very short-term ramifications and you may be sacrificing a year or two down the road, you're not always going to be in contention. We recognize that. Tony [La Russa] pushes these guys to be successful. My job is to make sure he has the right players to do so."

Oakland, meanwhile, is in fourth place in the American League West, 16 games out despite an aggressive offseason that included acquiring Holliday. The A's faced the possibility of losing him for nothing, if they chose not to offer him arbitration and risk the hefty one-year salary in case Holliday accepted. In picking up Wallace, Mortensen and Peterson, all second-round picks or higher within the past two years, the A's hope they have brought in a haul better than they would receive even from compensatory Draft picks.

For Holliday's part, he goes from last place to first. He hurried from New York, where the A's were continuing a four-game series against the Yankees, to Philadelphia by train on Friday afternoon.

"I'm really excited," Holliday said. "That's what we play for. I had a chance to taste it once, being able to play in the playoffs and in a World Series. Being able to play in meaningful games in September and October, you can't beat it. The atmosphere and the enthusiasm for baseball, the feeling you get as a player, the excitement about going to the field every day, I'm excited."

Holliday has long been a target of the Cardinals, who talked trade with Colorado over the offseason before the Rockies shipped the three-time All-Star to Oakland. He bolsters the team's outfield and offers the cleanup hitter that manager La Russa has long coveted to slot behind Albert Pujols in the Cardinals lineup.

Moreover, he represents a massive upgrade in left field, which has been a major problem for the Cardinals in 2009. Overall, Cardinals left fielders have batted .212 with a .294 on-base percentage and a .342 slugging percentage in '09.

"It really deepens our lineup," La Russa said. "You start talking about Matt, and you have Mark here, and that makes us deeper. That's one of the keys to improving the offense is to get deeper. The guy that protects Albert is the guy you don't want to face. Whatever he does, he does it well. Matt Holliday -- he's a tough out. So we're better. It makes our lineup deeper, that's how we look at it. It makes everybody better, because it's more tough outs."

For his career, Holliday is a .315 hitter with a .385 on-base percentage and a .541 slugging percentage. He won the National League batting title in 2007, when he was also runner-up for MVP honors. The right-handed hitter has won three Silver Slugger Awards and was the most valuable player in the 2007 National League Championship Series.

However, his numbers in Oakland have not been up to his usual standards. In 93 games with the Athletics, Holliday put up a line of .286/.378/.454, a far cry from his usual NL rates. Not only has he needed to adjust to a new league, but he also no longer has the benefit of playing half of his games at the Rockies' extremely hitter-friendly Coors Field.

The flipside of that, though, is that Holliday has come on strong since a slow start. Since May 11, his numbers are more in line with his career performance. He's hitting .316 with a .420 OBP and .489 SLG over that 65-game stretch. He hopes that getting back to the National League will help with that renaissance.

"I'm extremely excited," Holliday said. "I feel very blessed to be back in a pennant race, on a great team with a great organization. Obviously I'm very thankful for my team in Oakland. Those guys were great and I have a lot of special relationships with teammates now. But I'm excited to be here and to be back in the National League."

Wallace, 22, was St. Louis' first-round pick in the 2008 First-Year Player Draft and has rocketed through the Minor Leagues. He is currently playing at Triple-A Memphis, with a line of .293/.346/.423 in 62 games. Wallace is currently a third baseman, but uncertainty exists as to whether he will stick at that position. If Wallace cannot play third base, that limits him to first -- a position where the Cardinals are plenty well set, given the presence of Pujols.

"I would say it this way: there was an internal debate if he would be an everyday third baseman," Mozeliak said. "Frankly, he was playing well, but there's still one more level."

Mortensen, 24, is also at Memphis and was a supplementary first-rounder in 2007. Like Wallace, he rose very rapidly through the St. Louis system, but he has not overwhelmed hitters in the high Minor Leagues. This year at Memphis, Mortensen is 7-6 with a 4.37 ERA, 82 strikeouts, 34 walks and 11 home runs allowed in 105 innings.

Peterson, 21, was a second-round selection in 2008. The lefty-swinging Long Beach State product is another fast-promoted player, having reached Double-A in his first full professional season. He's batting .295 with a .361 OBP and .421 SLG on the year, with most of the season spent at Class A Palm Beach.

It's the second major deal between St. Louis and Oakland in five years. After the 2004 season, the A's acquired Dan Haren, Daric Barton and Kiko Calero from the Cardinals for Mark Mulder.

Holliday will wear No. 15 for the Cardinals. That number is currently worn by hitting coach Hal McRae but is best known in St. Louis as the number of Jim Edmonds from 2000-07.

In his first at-bat with the Cardinals on Friday against the Phillies, Holliday legged out an infield single. He then stole second and came home to score on an RBI single by Rick Ankiel.