49ers.com's training camp positional previews continue with a look at the tight ends on the roster. Two of the team's prominent pass-catchers at the position enjoyed career-best seasons in 2015. Will that production continue under Chip Kelly in 2016?
Returners:

Busta Anderson, Blake Bell, Garrett Celek, Je'Ron Hamm, Garrett Celek. Newcomers:

Bruce Miller (current fullback, moonlighted as pass-catching tight end this offseason)What we know:

Celek and McDonald seized opportunity after last season's trade of Vernon Davis to the Denver Broncos. Both young pass-catchers produced career-high numbers in 2015. Celek signed a four-year contract extension in the offseason after he caught 19 passes for 186 receiving yards and three touchdowns, which tied McDonald for second most on the team. But after Celek suffered a season-ending ankle injury, McDonald finished the year strong. He caught 30 passes for 326 receiving yards and three touchdowns of his own. McDonald caught 21 passes and his three scores in the final seven games of the season.

Bell, too, enjoyed his best games in the second half of the regular season. The converted college quarterback out of Oklahoma caught 15 passes for 186 receiving yards as a rookie. Bell's first NFL campaign included three games where he surpassed 43 receiving yards.

Miller (76 career receptions) has established himself as a reliable option in the passing game in the five-year span that he's worn a 49ers uniform. Kelly's coaching staff moved the fullback into a more prominent pass-catching role this offseason. Miller hasn't fully converted to tight end, but for all intents and purposes in Kelly's scheme, Miller can be looked at as a hybrid player who can wear many hats.What we'll find out:

Is Miller really a tight end? Or will it even matter what abbreviated positional letters are next to his name? As long as Miller is open and hauls in passes, the 49ers quarterbacks aren't likely complaining about his position designation. The truth is, we observed Miller go through individual drills with tight ends throughout the offseason. He also spent time in the meeting rooms with the position group, unlike prior years where he worked exclusively with running backs coach Tom Rathman's crew. The upcoming camp practices will give added perspective to Miller's role with the team going forward.

We'll also get a better sense of who is getting first-team reps between Celek and McDonald. Additionally, camp will offer opporunities for young players like Bell, Anderson and Hamm to assert themselves and get into the conversation for added playing time in presason games.Quote of the offseason:

"My first day in here, I went to the back with the running backs and Tom told me, 'You're going to sit over there with those guys.' That was the first time I heard about it." Miller on how he learned he'd be working with the tight ends this offseason.