The Los Angeles Chargers are still hoping that first-round pick Mike Williams, who has shown some encouraging signs after receiving a second epidural, will not need surgery on his herniated disk, league sources tell ESPN.

The rookie wide receiver recently was given the epidural in a last-ditch effort to get him ready at some point during training camp, but sources said he is not expected to be available for the start of camp and there is concern he could need season-ending back surgery.

Another source is optimistic that Williams will not need surgery and said Thursday afternoon, "He's been coming along pretty well."

Mike Williams might need surgery on a herniated disk that would sideline him for his rookie season. Kelvin Kuo/USA TODAY Sports

Williams was diagnosed with the herniated disk after his first practice during rookie minicamp and did not practice again. Chargers coach Anthony Lynn told reporters in the spring he hoped Williams' back would quiet down enough with rest that he could be ready for training camp.

Williams has experienced some positive results from the second epidural, but there still are concerns and uncertainty about how his back will respond this summer.

The Chargers remain uncertain about when Williams initially injured his back. One source said it's possible it was injured at the combine and during his pro day but he did a good enough job masking it so that teams would not know and his draft stock would not be affected.

The Chargers selected Williams with the seventh overall pick, and he showed up in Los Angeles with a bad back.