The Detroit Lions continue to talk up a running game that ranked 30th in the NFL last year, all while searching for possible help for the position.

Lions coach Jim Caldwell expressed his confidence in injured running backs Ameer Abdullah and Theo Riddick returning to form before the start of rookie minicamp Friday.

Both Abdullah (foot) and Riddick (wrists) are coming off season-ending surgeries, and the Lions did not take a running back in last month's draft as insurance.

"I think overall we’ve got some pretty good depth there," Caldwell said. "Now, do we look to improve anytime that we can? You better believe it. Anytime we can, we look and we see if it fits us and if it does we’ll make the decision, if not we move on."

Related:Detroit Lions mum on possible interest in LeGarrette Blount

Veteran Matt Asiata is among the tryout players taking part in practices Friday-Sunday as the Lions try and determine whether to add him to their backfield competition.

Asiata played the last five seasons for the Minnesota Vikings and would add another goal-line threat to the Lions' roster.

He ran for 402 yards and six touchdowns last season.

Caldwell declined to say what Asiata needs to do to win a job this weekend, but he praised his toughness and versatility.

"I think anybody knows who’s seen him work, he’s a good special teamer, he’s tough, he’s a very good pass protector," Caldwell said. "He carries the ball and he runs behind his pads. He’s always been a very, very effective player in this league."

Caldwell also declined to say if the Lions have any interest in LeGarrette Blount, the top running back left in free agency. Blount led the NFL with 18 touchdowns last year, but his situation was complicated by the New England Patriots placing a little-used veteran free-agent tender on him earlier this week.

The tender means Blount will factor into the compensatory draft pick formula if he signs elsewhere, and the Patriots have the right to match any offer he receives.

"We don't discuss those things," Caldwell said when asked about the Lions' interest in Blount.

The Lions averaged just 81.9 yards rushing per game last year, fewer yards than they averaged when they finished last in the league in rushing in 2015.

Abdullah had just 101 yards on 18 carries before he was lost for the season, and Riddick missed six games with ankle and wrist injuries.

The Lions also return Zach Zenner and Dwayne Washington from last year.

"I believe Ameer Abdullah, when he’s healthy and rolling, he’s awfully good," Caldwell said. "All you have to do is just take a look at the numbers. Don’t listen to me, look at the numbers and see when he’s on the field for you what he does. When Theo’s out there healthy for us, everybody knows what he can do. Those guys create a punch.

"And I don’t think anybody in this room has a question whether or not Zach Zenner can run the ball. We’ve got a young guy in Dwayne Washington nobody really knows how good he can be. But he has talent, he has ability, we like what we see in that particular area and he’s developing. He’s coming along."

Lions sign 8 draft picks, add 14 undrafted free agents

Contact Dave Birkett: dbirkett@freepress.com. Follow him on Twitter @davebirkett.

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