But that also means that he's been around long enough to have a better feel for his impact on his new team's offense. And it's significant. Even in the midst of an offensive slump, the Cardinals are still scoring at a much brisker clip with Holliday than they were before he arrived.
That's not just Holliday, of course. One day before the outfielder arrived, St. Louis acquired Julio Lugo from Boston, and Lugo has provided a boost as well. But Holliday, who's hitting over .350 since he was traded from Oakland, has been the biggest piece. The Cardinals were scoring 4.37 runs per game before Holliday arrived. From the day of the trade through Tuesday, they're at 4.81 per game.
Albert Pujols has been doing it all season, but now he has some star-caliber help right behind him in the No. 4 spot in the order.
"[Holliday's] got a terrific mentality at the plate," manager Tony La Russa said. "He goes up there aggressively to make something happen. He handles a lot of different pitches. He uses the whole field. That's a classic run producer. And you put him behind Albert, that's a tremendous [combination]. There's a lot of depth in that lineup, and adding Matt there has been huge for us."
Holliday's surge in St. Louis stands out in part because his numbers before the deal were somewhat pedestrian, at least by his high standards. It's not as though he was struggling before. He'd dug out from an early season hole, and he was getting his stats back to where they customarily stand. But his return to the National League has provided a perfect backdrop for a former batting champion to reestablish his prominence.
On May 10, Holliday was batting an ugly .226 for the A's. His OBP was .282 and he was slugging an unimpressive .383. He needed to get sorted out, and he did. He reincorporated a leg kick that he had tried to do without. Things started to feel natural again. And Holliday started to hit like a natural again. Although the A's sank, Holliday surged. From May 12 until the trade, his line was a much more familiar .316-.420-.489.
"I was trying to eliminate my leg kick and see if I could just stride," Holliday explained. "I was trying to stay with it, but it just wasn't going very well. So when I realized that [the kick] was an asset to me to go ahead and do it -- that it wasn't hindering me, it was helping me -- once I got back to doing that and got comfortable with it, I started to produce again."
He's improved upon his scorching pace since coming back to familiar turf, which has surprised exactly no one with the Cardinals. Holliday has long been a favorite of La Russa's.
"He's gotten base hits like a high-average hitter, which is left-field line to right-field line," La Russa said. "He's hit the ball for distance. He's hit the ball extremely hard. He's got a real quick bat. ... He's an excellent baserunner for a big guy. He steals bases. He's got good speed. He competes every day."
When Holliday arrived in St. Louis, much of the talk was that he'd "protect" Pujols, keeping opponents from pitching around the two-time MVP. Yet at first, Pujols slumped. Lately, though, Pujols has come on strong. And the intentional walks have tailed off. Pujols has received eight in 49 games since the trade, compared to 34 in 95 games before.
Overall, though, Pujols' production has been virtually identical with and without Holliday. What Holliday has done is to deepen a lineup that had a couple too many holes before his arrival. Yadier Molina and Ryan Ludwick can be more complementary offensive players, while either Rick Ankiel or Colby Rasmus comes off the bench most days.
It's a better team with Holliday, and that was the point. And as for the player himself, he's having a grand time playing for a winner, and he's enjoying being part of the St. Louis lineup -- even if it is in a bit of a slump right now.
"I think you have to have production up and down your lineup to be a successful team," Holliday said recently. "Because there's going to be nights when Albert and I don't do much. But when you have guys up and down who can come up with big hits and get on base and find ways to score runs, it makes for a better offense."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.