ALLEN PARK, Mich. (AP) -- His days in Detroit over, Ndamukong Suh still might help the Lions at defensive tackle.

While Suh is training with the Dolphins, his offseason workout partner, Caraun Reid is taking a big step toward replacing him in the middle of the defensive line.

"I'm in the best shape of my life," the second-year player said. "I'm 10 pounds lighter than I was a year ago, I lost 3 percent of body fat, I'm lifting more and I'm a lot quicker."

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Reid said it was tough adjusting to Suh's workout schedule, but he thinks it was worth it.

"It took a while, but I learned that I was able to keep up with his progressions," Reid said of the workouts, although he wouldn't reveal the locations. "At the end of the day, it was good. I'm a better man for it."

Lions coach Jim Caldwell noticed in the spring that Reid was making a major effort to improve his speed and strength, and is quite happy with the results.

"You know, you can tell, not only has he changed physically, just in terms of his overall body comp, but his strength, his explosiveness has also improved," Caldwell said. "He's playing well. That's kind of what you see typically from a guy who's going into his second year that's worked extremely hard in between to try to get to the point where he measures up to what this league requires. So he made a pretty sizable leap physically, and also you can see it in his play now."

His teammates have noticed as well. Reid faced veteran Manny Ramirez in one-on-one drills during Monday's padded practice, and held his own.

"He's doing a nice job," Ramirez said. "It's tough to judge from practice, because we are going against each other all the time, but he's giving me a hard time out here."

That will change Thursday when the Lions face the Jets.

"It will be a good test for all of our players to face someone other than their teammates," Caldwell said. "It is a much more accurate judgment of skills when you see players going against someone whose moves they don't already know."

Reid and Tyrunn Walker will get plenty of time against New York, but when the regular season arrives, they will be fighting for the spot next to Haloti Ngata. Ngata, the player the Lions hope to provide the most help replacing Suh and Nick Fairley, hasn't taken part in camp because of a hamstring injury. Caldwell expects him back well before the season opener.

That leaves Reid and Walker as the favorites to replace Fairley.

"Walker is a real fine athlete, big guy who can run, has experience and very versatile, so that's a real good battle in there between those two guys," Caldwell said. "It will be interesting to see how they respond."

As for Reid, he knows what is at stake.

"This is the biggest preseason of my life," he said.