Washington Redskins coach Mike Shanahan issued a public challenge Monday to left tackle Trent Williams, saying the 2010 first-round draft pick needs to continue his on-field development and demonstrate improved commitment and maturity following his drug-related suspension. The coach also said he sees a change in tight end and /free-agent-to-be Fred Davis, who also ended the season on a four-game suspension for failing multiple drug tests.

A dejected Trent Williams after the Redskins lost to to the Dallas Cowboys 18-16 on Sept. 26 in Arlington. (Toni L. Sandys/Washington Post)

Shanahan said that Williams showed improvement both in his play and his work ethic this season. But the failed drug tests put a dark cloud over any positives Williams produced this year.

“He’s got to be smart enough to understand that if you disappoint your football team like you did, you’d better come back with a passion and the drive to do what we need him to do, especially being the fourth pick of the draft,” Shanahan said. “We know the talent he has, we know he’s a likeable guy. I was pleased with his work ethic coming into his second year, how he was playing, but he’s got to prove that he can do it on a day-to-day basis and set the standard for our football team and our organization.”

Davis, meanwhile, is eligible for free agency after playing the final season of the contract he signed as a second-round draft pick in 2008. Davis had a breakout year this season, recording 59 receptions for 796 yards in 12 starts – all career highs. He also had three touchdown catches.

He and Williams were among 11 NFL players who failed drug tests for recreational marijuana use following the end of the league’s lockout. Only Williams and Davis continued to fail drug tests over the course of the season.

Davis likely has hurt his chances of earning a lucrative, long-term deal. One more failed drug test would result in a one-year suspension for him. (The same goes for Williams, but he is under contract for next year).

But Shanahan said that he isn’t judging Davis more harshly because of the suspension.

“Fred made a mistake. We sat down and talked about his mistake. I do feel very good about Fred as a person,” the coach said. “I like the way he worked, I like his attitude. I like his development over the last year-and-a-half since I’ve been here. I think he’s had a complete change in the way he handles himself off the field, to preparing himself to be a consummate pro, to working out, and hopefully the mistake won’t happen that he made this year.”