COSTA MESA, Calif. -- Tyrell Williams says he believes he's a true go-to receiver in the NFL, and he'll see how much others agree when the top unrestricted free agent for the Los Angeles Chargers hits the open market in March.

"I definitely feel like I'm a No. 1 receiver," Williams said while cleaning out his locker at the end of the season two weeks ago. "So I want to make sure that I clean up all of the little things in route running and blocking, to make sure I solidify myself as a No. 1."

For the most part, Williams did not get the opportunity to show that with the Chargers because of Keenan Allen, one of the top receivers in the NFL.

Still, as an undrafted rookie out of Division II Western Oregon in 2015, Williams exceeded expectations during his four years with the team.

"This past year, his game had already been solid, and he kind of took it to the next level this year," Chargers general manager Tom Telesco said. "He's certainly earned his second contract. Those are discussions we have to have, but I just don't have hard answers at this point in the offseason."

2019 NFL Free Agency Here's what to know:

• Most impactful moves for all 32 teams »

• Barnwell's lessons from free agency »

• Barnwell's grades: Tracking big moves »

• Winners and losers from free agency »

• Picking underrated, overrated signings »

More coverage » | Back to NFL »

Williams finished with 41 catches for 653 receiving yards and five total touchdowns in 2018. He totaled 155 receptions for 2,530 receiving yards and 17 total touchdowns in four years.

With Allen out for the season because of a torn ACL knee injury, Williams had his best season in 2016, leading the team in receptions (69), receiving yards (1,059) and tying for the team lead with seven receiving touchdowns.

Williams has shown toughness, playing through injuries without missing a game in his career.

During the offseason, he says he usually goes back and watches every game, evaluating things he needs to improve.

"It's been big," Williams said. "I try to always be critical with myself, just seeing stuff I want to get better at. I try to get better at everything. But I also try to pick out some specific things to focus on in the offseason, so I think that's been huge for me."

The Chargers would like to have Williams back, but the free-agent price tag could get too steep. Last year in free agency, Sammy Watkins signed a three-year, $48 million deal that included $30 million in guaranteed money with the Kansas City Chiefs. The Rams traded with the New England Patriots for Brandin Cooks, signing him to a five-year, $81 million contract extension that included $49.46 million guaranteed money. And Paul Richardson left the Seattle Seahawks to join the Washington Redskins in free agency, signing a five-year, $40 million deal that included $16.5 million in guaranteed money.

The Chargers have a replacement for Williams already on the roster in big-body receiver Mike Williams, who had a breakout season in his second year out of Clemson.

Possible landing spots that could make sense for Williams include a return to the Pacific Northwest with the Seahawks or joining former receivers coach Nick Sirianni and offensive coordinator Frank Reich with the Indianapolis Colts.

"We'll see [what happens]," said Williams, when asked about returning to the Chargers. "You never know. I'm just going to let my agent take care of it and try and enjoy these next, couple months."

According to ESPN Stats & Information research, the Chargers have $22.8 million in salary cap space, which puts them in the bottom half of the league.

Including Williams, the Chargers have 14 unrestricted free agents, including Pro Bowler Adrian Phillips, nose tackle Brandon Mebane, linebacker Denzel Perryman tight end Antonio Gates, backup quarterback Geno Smith and versatile defensive lineman Damion Square.

"Anybody that has watched us build our team over the last couple of years -- I think you can see that we like to draft, develop and re-sign our own," Telesco said. "And then be very selective in free agency with [signings like center] Mike Pouncey, [tackle] Russell Okung, [cornerback] Casey Hayward and others.

"We like to retain our own. I think we have a good core here. Is it realistic to keep every single player? It's not, but these are discussions that we will have in the next couple of weeks as far as these are the resources we have under the cap and this is how it's going to fit."

Unrestricted free agents (14): WR Geremy Davis, LB Kyle Emanuel, TE Antonio Gates, P Donnie Jones, DT Brandon Mebane, LB Denzel Perryman, S Adrian Phillips , DT Darius Philon, LB Hayes Pullard, QB Geno Smith, DT Damion Square, CB Jason Verrett , S Jaylen Watkins, WR Tyrell Williams.

Restricted Free Agents (1): CB Trevor Williams.

Exclusive rights (3): DE Isaac Rochell, WR Artavis Scott, C Cole Toner.