5. Marcin Gortat, UFA
2013-14 Stats: 13.2 PPG, 9.5 RPG, 1.7 APG, 54.2 FG%, 17.6 PER
The Washington Wizards could lose two-fifths of their starting lineup in free agency this summer between center Marcin Gortat and swingman Trevor Ariza. The two are expected to command somewhere between $15 million and $20 million per year, likely on three- or four-year deals, per Grantland's Zach Lowe.
Both should have multiple suitors pursuing them, but Gortat is clearly the more irreplaceable of the two. Gortat is an expert screener, which is crucial for Washington's pick-and-roll heavy attack with John Wall and Bradley Beal, and while he's not a stretch 5 like Chris Bosh or Pero Antic, he's not completely lost offensively when drawn away from the rim.
4. Pau Gasol, UFA
2013-14 Stats: 17.4 PPG, 9.7 RPG, 3.4 APG, 48.0 FG%, 19.3 PER
Pau Gasol is almost the polar opposite of Gortat in the free-agent market. He's nowhere near the defender Gortat is, but he's much more of a versatile offensive threat, both in terms of shooting range and floor vision.
Gasol has long been an expert passer, as evidenced by his career rate of 3.3 assists per game, and having a big man who can help run the offense makes life especially complicated for opposing defenses.
He's not a strong three-point shooter by any means (24.7 percent over his 13-year career), but he drilled 44.7 percent of his attempts from 10-16 feet this past season, helping provide invaluable floor spacing.
3. Tim Duncan, Player Option
2013-14 Stats: 15.1 PPG, 9.7 RPG, 3.0 APG, 49.0 FG%, 21.3 PER
Without regard to age, Tim Duncan would be challenging Bosh for the No. 1 spot in the free-agent center rankings. The timeless 38-year-old posted per-36-minute averages right in line with his career marks (18.7 points, 12.0 rebounds, 2.3 blocks) this past season, proving once and for all that he is indeed an automaton.
Fresh off his fifth NBA championship, it may be tempting for Duncan to end his illustrious career on a high note. However, the San Antonio Spurs are "quietly operating under the assumption that Duncan and [head coach Gregg] Popovich will indeed be back next season," according to ESPN.com's Marc Stein.
With "one for the thumb" now secure, Duncan can finally set his sights on tying Michael Jordan's championship count. But because he's unlikely to play for more than another year or two (and there's zero chance of him leaving the Spurs if he doesn't retire), he takes a slight tumble in the free-agent center rankings.
2. Greg Monroe, RFA
2013-14 Stats: 15.2 PPG, 9.3 RPG, 2.1 APG, 49.7 FG%, 18.1 PER
The Detroit Pistons are damned if they do, damned if they don't when it comes to Greg Monroe's impending free agency. Letting an offensively gifted 24-year-old big man walk for nothing could be devastating for Detroit's ongoing rebuild, but overpaying him to stay might be even worse, especially if the Pistons can't find a taker for Josh Smith on the trade market.
Smith, Monroe and Andre Drummond failed to develop chemistry in 2013-14—the trio had the third-worst plus-minus rating of any three-man lineup that played at least 1,200 minutes—but that's not necessarily a condemnation of Monroe.
He and Drummond worked well alongside one another the previous season; the addition of a third non-floor-spacer is what caused Detroit's offense to sputter so badly.
Teams with an elite shot-blocker—hello, New Orleans—would be wise to pursue Monroe this summer. He's not going to become a three-point sniper overnight, but he can provide floor spacing, as he knocked down a career-high 41.0 percent of his attempts from 10-16 feet this past season.
1. Chris Bosh, ETO
2013-14 Stats: 16.2 PPG, 6.6 RPG, 1.1 APG, 51.6 FG%, 19.0 PER
Like his fellow Big Three members, Bosh possesses an early termination option in his contract that would allow him to become an unrestricted free agent this summer, if he so desires. He seems to be in no hurry to leave the Miami Heat, however.
"I don't want to go anywhere," Bosh told Dan Le Batard during a radio interview in late May, per ESPN.com's Brian Windhorst. "I like it here. It's Miami. Everybody wants to come here."
When asked if he'd be willing to take a pay cut to keep the Big Three together—or even to add another high-profile member to the mix—Bosh simply replied, "If that's what it takes." For a man who's sacrificed so much since joining Miami—from his shot selection to his defensive positioning—Bosh sounds willing to keep making concessions in exchange for annual chances to compete for championships.
If the oft-criticized big man decides to opt out, he'll have no shortage of suitors on the free-agent market. His ability to space the floor offensively—he drilled 74 three-pointers this year, 24 more than his first seven seasons combined—and defensive foot speed makes him one of the most valuable two-way big men in the league, despite what his critics might otherwise believe.
Honorable Mentions: Andray Blatche, UFA; Spencer Hawes, UFA; Emeka Okafor, UFA
Unless otherwise noted, all statistics via Basketball-Reference.com or NBA.com/stats. All contract information via Spotrac.