"He plays the game the way it's supposed to be played," said Kaline, who is currently a special assistant to Tigers general manager Dave Dombrowski. "He has tremendous ability and I expect him to go on -- if everything goes right -- to be one of the best players that ever played this game."
Entering Friday's action against the Brewers, Harper, now in his second year in the big leagues, is one of the best players on the Nationals, hitting .276 with 15 home runs, 35 RBIs and a .372 on-base percentage. He missed more than a month of action after he slammed his left knee into the right-field wall at Dodger Stadium on May 13.
Kaline doesn't see Harper reaching a middle ground to avoid injuries.
"If you pop up to the infield, you know it's going to be an easy out, you don't go 110 percent. You make sure you get on base and may get the extra base," Kaline said. "And of course ... the walls ... he is fortunate now that he plays the outfield where the walls are all padded. When I played, they were concrete.
"There are times -- instead of going full belt into the walls, where he might hurt himself for good -- you have to be careful. But you can't teach that. He's got to play the way he is taught and the way he has always played. He would probably feel he let the fans down if he didn't go hard all the time."
Kaline and Harper share something. They both entered the big leagues as teenagers and became major players early on. At 19, Harper helped the Nats win the National League East title and won the NL Rookie of the Year Award. At 20, Kaline won the American League batting title.
In Kaline's opinion, Harper is much stronger than he ever was.
"I've been fascinated by what he has been able to do. He's much more stronger than I ever was, because I was 150, 155 pounds," Kaline said. "The only thing I would tell him is respect the game -- which it looks like he does -- take care of his body, be a good team player. If you leave this game as a good team player and gain the respect of your teammates, then you have done a great job. I know he is going to go all-out. I just hope that he stays healthy."
Kaline is impressed with Harper's swing. The Hall of Famer believes Harper is capable of winning the home run title. Kaline is not sure if the outfielder can win a batting title like he did in 1955.
"It looks like to me that he swings for home runs," Kaline said. "To me, if you swing for home runs a lot, you are not going lead the league in hitting. He is certainly capable of doing both if he puts his mind to it. He is trying to do what the team thinks he needs to do, whether it's a power hitter, he will probably try and do that. ... Whether he is able to [win the battle title and home run title], I don't know, because he is very, very aggressive at the plate."