ALLEN PARK -- How will the Detroit Lions replace Anquan Boldin?

Through two days of practice, the answer often appears to be with no receiver at all.

The Lions have been rolling with a lot of two-tight end sets in training camp, even as Eric Ebron nurses a sore hamstring. Darren Fells and Cole Wick were in the starting lineup to open practice Monday, alongside Golden Tate and Marvin Jones.

Fells in particular had a tremendous practice, working both sidelines for catches and beating Tahir Whitehead for another over the middle. He even got loose behind the defense during team work, and ripped the ball from safety Tavon Wilson for a deep completion.

"I told Matt, 'I'll catch it if you throw it to me,'" the 6-foot-7 Fells said. "Throw it high, and I'll get that rebound."

Detroit Lions training camp - July 31, 2017 50 Gallery: Detroit Lions training camp - July 31, 2017

Fells meant that literally. He turned down football offers to pursue basketball at UC Irvine, and left as the school's third-leading rebounder. He then spent five years playing professionally abroad, including in Belgium, Finland and Argentina.

He eventually returned to the U.S. to give football try, and after a brief dalliance at defensive end, settled in as a tight end for the Cardinals the last three years. He was never much of a pass catcher, topping out at 21 receptions in 2015, and was instead known more for his blocking.

But coach Jim Caldwell stressed upon Fells' arrival in Detroit that he could be a two-way player, and in the early going, Fells certainly looks the part. He doesn't have Ebron's speed, but he moves well enough and the hands seems sure.

"He's a bit more mobile than what you can expect and anticipate," Caldwell said. "He can catch the ball, he can do it in a number of different areas and today he had a couple pretty nice catches. He's working at it, he's getting better, big target."

The Lions entered the offseason looking to acquire the kind of pieces that would allow them to expand their two-tight end sets. Stafford completed 22 of his 26 passes out of such looks last year, but Detroit couldn't roll with them more because of personnel constraints.

But with Fells aboard, plus fourth-round pick Michael Roberts and a new-look Cole Wick -- his weight gain is readily apparent -- the Lions seem to have cultivated some intriguing depth at the position.

"You have to do things according to what your personnel grouping allows and your best players allow in that regard," Caldwell said. 'So, yeah, we do have a few more guys at that (tight end) spot. So, we are going to be able to incorporate maybe a little bit more.

"Oftentimes those things go game by game, depending on what we face, but we certainly do have some possibilities."