Under contract: Emil Igwenagu (2016)
Free agents: Jed Collins (UFA)
Currently, Emil Igwenagu is the only fullback under contract for the Lions. He spent last season on the practice squad, and he was signed to a futures deal after the 2014 season. In all likelihood, he was brought back as extra depth more than anything since he is not expected to suddenly step in as the Lions' starter at fullback.
The starting role at fullback will likely belong to Jed Collins for at least another season. The Lions have to actually re-sign him first, but there's no reason to think that Collins won't be back in Detroit in 2015. He did a good job in the fullback role in Joe Lombardi's offense last season, and he also contributed on special teams. With a minimum type of deal likely coming his way, re-signing Collins should be a pretty straightforward move for the Lions.
Need going forward?
As long as the Lions re-sign Collins, there won't be any need for additional help at fullback. Bringing in an undrafted free agent to compete at this position would be wise, but chances are the starting spot will be set the second Collins is re-signed.