A lot of negative things happened for the Detroit Lions on Sunday. They not only had their winning streak snapped in an ugly loss to the San Francisco 49ers, but they also lost running back Jahvid Best to another concussion, according to Chris McCosky.

Best went missing from the game in the fourth quarter and fans were not given an explanation about what happened to him. It wasn't a huge story at the time, but several people on Twitter and in the game threads were wondering if he was hurt. As it turns out, he was in fact injured.

Things got worse for Best in the fourth quarter. He sustained a concussion, his second of the year (he had one in training camp), after a 1-yard run. 

Best was in the locker room after the game, but was not allowed to talk to the media per NFL policy. The Lions did confirm that Best was concussed.

Best's first concussion this year happened during a preseason game against the Cleveland Browns. It didn't keep him out for very long, but that was merely the silver lining in an otherwise bad situation. Best dealt with concussion issues in college, and now he has suffered another one.

Lions linebacker Justin Durant has missed the last three games because of a concussion, and tight end Tony Scheffler was out this week because of a concussion. Right now there is no indication of how long Best will be out with his concussion.