Are 49ers in the market for an inside linebacker?

With the stunning retirement Monday night of Chris Borland, less than a week after Patrick Willis called it quits, the San Francisco 49ers currently have three inside linebackers with NFL experience on their roster.

Michael Wilhoite started 18 games.

Nick Moody started the last two.

And NaVorro Bowman is still trying to come back from the gruesome knee injury he suffered in the NFC title game in January 2014.

The 49ers suddenly need help at inside linebacker, a position that was supposed to be a strength for Jim Tomsula's first year as an NFL head coach. Instead, the Niners need depth, possibly a starter, and the position is one of need.

So as the new league year and free agency enters its second week, the 49ers had more than $5.07 million in cap space, per ESPN Stats & Information, Monday morning, before Borland's announcement to Outside the Lines went public (Borland had a cap value of less than $695,000).

A look, then, at three intriguing inside linebacker possibilities still on the market who might bolster the Niners' unit:

Rolando McClain -- Bay Area fans who had enough of Ro' in his three years as a bust with the Oakland Raiders, who made him the No. 8 overall pick of the 2010 draft, might be pleased to find how much he seemingly matured last season with the Dallas Cowboys in tying for second in the league's Comeback Player of the Year voting. He's still only 25 -- yes, he's retired twice -- and his 108 tackles ranked second on the team, despite missing four games -- he was inactive for three and missed one with a knee injury. He also had one sack, nine tackles for a loss, five quarterback pressures, two interceptions, six pass deflections and a forced fumble. Concussions, though, knocked him out of the Cowboys' two playoff games. Perhaps most intriguing -- while he was miscast as a middle linebacker in the Raiders' 4-3 scheme, he starred at Alabama inside its 3-4, the same alignment used by the 49ers.

Pro Football Focus grade: 13.9 (highest among remaining UFA LBs)

Lance Briggs -- Remember him? The 12-year veteran and seven-time Pro Bowler might be a little long in the tooth for the Niners' liking at 34 but he does have pedigree and presence. Even if he missed the Chicago Bears' last five games with a groin injury and three games earlier in the season with a rib injury. He earned $4.75 million in base salary last year, when he had 63 tackles, an interception and a forced fumble with two pass breakups and a QB pressure in eight starts, but is not expected to command that much this year. Plus, Briggs has been breaking down, having missed seven games in 2013 with a fractured shoulder. Before that, he had at least 100 tackles in nine straight seasons (2004 through 2012) and has 16 career interceptions, 15 sacks, 19 forced fumbles and seven fumble recoveries. His six defensive touchdowns in 170 starts over 173 games are the third-most in Bears history.

Pro Football Focus grade: 7.6 (2nd-highest among remaining UFA LBs)

Brandon Spikes -- Spent the first four years of his career with the New England Patriots before playing last season with the Buffalo Bills on a one-year, $3.25 million contract. He started 10 games for the Bills and had 54 tackles, one sack and a forced fumble. Spikes is more of a run-stopping linebacker, which the Niners need in the middle, but considered to have limited range as a pass defender, coming off the field in most of the Bills' passing situations. In fact, he played in just 46 percent of the Bills' defensive snaps. Spikes, you'll recall, was a second-round pick of the Patriots in 2010 and after being placed on injured reserve before the 2013 playoffs, he accused New England of violating injury-reporting rules. The NFL cleared the Patriots.

Pro Football Focus grade: 7.3 (3rd-highest among remaining UFA LBs)

ESPN.com Cowboys reporter Todd Archer, Bills reporter Mike Rodak and Bears reporter Michael C. Wright contributed to this report.