It turns out that Justin Miller wasn't the only cornerback who signed with the on Wednesday. The Lions have also signed cornerback Drew Coleman to a one-year deal, according to the team's official website.
Unlike Miller, Coleman is primarily a cornerback and not a return specialist. Also unlike Miller, Coleman has actually played in the NFL in recent years. He spent last season with the Jacksonville Jaguars, and before that he was with the New York Jets for five seasons. He has a total of four career interceptions, and in the last two years alone he has forced eight fumbles.
Coleman is much more likely to make the team than Miller given he actually appears to be a decent option at cornerback. He should be in the mix to lock down one of the spots at cornerback during training camp.
The Lions ended up releasing wide receiver Marcus Harris to make room for Miller. Right now, we're still waiting to hear who was released to make room for Coleman.
UPDATE: The Lions have released cornerback Ross Weaver to make room for Coleman, according to Tim Twentyman.