The addition of veteran cornerback Rashean Mathis could have a trickle-down effect in the Detroit Lions’ secondary which is still a work in progress.

Mathis, who was signed on Saturday, has fit in quickly. On Tuesday he took some snaps with the first team at nickelback.

“I know football,’’ Mathis said. “Inside there you just have to know the scheme of the defense, know the weaknesses and every now and then don’t be scared to stick your face in the fan.’’

Great line and spoken like a 10-year NFL veteran, to be sure.

“We value versatility. He’s a very experienced player and a very savvy player,’’ coach Jim Schwartz said. “It showed in his ability to pick things up quickly and be able to get him on the field. We haven’t had a lot of time to evaluate him physically. Some of those new guys that we have signed we have to get them ready to play this week and get a good look at them. Therefore we have been trying to get them some more reps during practice.”

In his 10-year career  with the Jacksonville Jaguars, Mathis has played safety, cornerback and nickel.

“Having that under my belt definitely helps coming into a system like this when you’re asked to do a lot of things,’’ Mathis said.

The Jaguars did not offer him a contract for this season.

Bill Bentley has played in the slot with the first team since camp started. Mathis’ addition doesn’t mean he will lose that spot, but he’s got more serious competition now.

Rookie Darius Slay has continued to work with the first team defense this week at cornerback. Previously veteran Ron Bartell had been with the starters.

Slay needs to show his stuff on Thursday against Tom Brady and the New England Patriots.

“Well we will see what happens in week three.,’’ Schwartz said. “He needs to take a jump this week. He’s going to have an opportunity to get more reps against some pretty good competition. A top-notch quarterback and a very good passing offense. It’s a very important week for him.”

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