Four years later, Pujols called Harper and Angels outfielder Mike Trout two of the most exiting players in the game of baseball.
"I'm pretty excited to see [Harper], to go against him in this series and see what he can do," Pujols said.
A lot of people are making a big deal about Harper and Trout facing each other for the first time. Experts have compared the two players ever since they entered the league full-time in 2012.
Asked if it's fair to compare the two players, Pujols said, "My advice as a veteran player is just play the game the way they know how to play it, and try to not get caught up too much into the media [hype]. … That's extra pressure you don't need. This game is already tough enough. Like I told Mike, he has to be himself, play the game he knows how to play. Don't try to do extra things special, because the normal things that you do are pretty special already."
Pujols was aware that Harper was taken out of the game for not hustling on Saturday against the Cardinals. Pujols said the same thing happened to him when he was a member of the Cardinals.
"[Then-manager] Tony [La Russa] took me to the side and told me, 'That's not me.' Sometimes you get caught up," Pujols said. "… [Harper] respects the game so much. He was probably one of the guys that was more down, because that's not him. It teaches you not to take this game for granted."
Pujols said every player goes through a point where they don't feel like going all out in a game.
"Everybody -- whether you are in Little League, high school or college -- we have all gone through that," Pujols said. "Hopefully, it doesn't happen to him again. Sometimes, you go through some things or you have an injury to the point where you have to lay back. When you hit a ground ball and you are going to be out by 30 feet, why are you going to try to bust your butt when you are hurt?
"There are a lot of things that could happen. I don't know his situation, but I know people are trying to make a big deal about it. … When you play 162 games, those are things that are going to happen. You just need to make sure that you clear your mind and be ready to play the next series or the next game.
"[Harper] admitted that he was wrong. He knows it. I'm pretty sure the next day he went out there and busted his butt and ran the bases hard."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.