LOS ANGELES -- The Los Angeles Rams still have a glaring need on their roster; one that directly impacts franchise quarterback Jared Goff.

They needs someone to snap him the ball.

The Rams released Tim Barnes, who started each of the past 32 games at center, as part of a series of cost-cutting moves a couple of weeks ago. And they're still in search of his replacement. They signed Ryan Groy to an offer sheet, but the Bills matched it. So the Rams have had to move on. They'll continue to look toward the free-agent market, but they will eventually look to manufacture some depth in-house, as well.

The only center on the Rams' roster is Demetrius Rhaney, a seventh-round pick from 2014 who has started only one game. New head coach Sean McVay recently said the Rams would look to "cross-train" some of their guards at center as a means to shore up the position.

Mostly, though, the Rams need help from the outside. On Monday, they hosted John Sullivan, one of few remaining free-agent centers who could be a fit.

He is among five key unrestricted free agents to watch at the position.

Nick Mangold has been to the Pro Bowl seven times. Tom Szczerbowski/Getty Images

Nick Mangold: Mangold is easily the most accomplished center available, having gone to seven Pro Bowls while missing only four games in a 10-year span from 2006 to '15. But Mangold, ranked 82nd on ESPN's list of the top 150 free agents , is 33 now, coming off a mildly surprising release from the rebuilding Jets. And injuries are now a major question. Mangold was limited to eight games last season. He suffered a severe ankle injury that nearly required surgery, returned after a four-game absence, then aggravated the injury and spent the final four games on injured reserve. Teams have asked if he would be willing to move to guard.

Tim Lelito: ESPN had Lelito listed as the 131st-best free agent, but he is perhaps better suited as a left guard. An undrafted free agent out of Grand Valley State in 2013, Lelito went on to start a combined 20 games for the Saints from 2015 to '16, with three of those coming as the center. Lelito can play there in a pinch, and he spent most of the 2014 offseason working out at center. So, perhaps he could be a cheap utility offensive linemen if the Rams can't find another fit. His 6-foot-4, 315-pound frame is certainly appealing.

Sullivan: He was considered one of the NFL's best, most under-appreciated centers from 2009 to '14, while starting 93 of 96 games for the Vikings. But then he missed the entire 2015 season because of a back injury, was released and joined the Redskins as a backup, starting only one game in 2016. One aspect that might work in Sullivan's favor: He spent that 2016 season operating under McVay, at that point the offensive coordinator.

Cody Wallace: Originally a fourth-round pick by the 49ers in 2008, Wallace spent his first seven seasons with seven different teams and wound up starting only six games. In 2015, Wallace started all 16 games for the Steelers at center while filling in for an injured Maurkice Pouncey and handled himself well. But then Wallace missed almost the entirety of the 2016 season with a knee injury, and now he's 32.

Ryan Wendell: Wendell was born and raised in Diamond Bar, which resides on the eastern part of Los Angeles County, and previously enjoyed a nice run with the Patriots, starting 44 games from 2012 to '14, most of them at center. For that, Wendell was named a captain heading into the 2015 season. But he appeared in only two games and finished that season on injured reserve, then spent the 2016 season buried on the Panthers' depth chart. Fickle game.