In news that makes a mockery of the NBA's decision to officially start its free agency period on Sunday at 6 p.m. ET, Kemba Walker has already reportedly agreed to sign with the Boston Celtics on a four-year, $141 million maximum contract. Somehow, before the Celtics are allowed to talk to any soon-to-be free agents, they have rebounded from the exits of stars Kyrie Irving and Al Horford, both of whom totally don't have commitments from other teams. Truly unbelievable stuff.

Walker, 29, is similar to Irving stylistically, but is renowned for his locker-room leadership and is more comfortable than Irving off the ball. In order to create cap room to sign him, Boston will have to say goodbye to free agents Marcus Morris and Terry Rozier. After last season's agonizing chemistry experiment, though, perhaps less is more when it comes to playmakers. Gordon Hayward should be healthier, and Jaylen Brown and Jayson Tatum should be happier. There is only one (giant, glaring) issue for the Celtics: They do not have a starting center. 

It is not just that Horford is walking. One of the reasons they had space for Walker is that Danny Ainge's front office dumped the reliable, defensive-minded Aron Baynes on draft night. Boston can use early bird rights to re-sign backup big man Daniel Theis, and the young Robert Williams III and Guerschon Yabusele could battle for a reserve role. Semi Ojeleye and rookie Grant Williams could theoretically play some small ball 5 if Brad Stevens wants to get weird, but the Celtics must try to use the $4.8 million room exception -- their only avenue to add another player on more than a minimum contract -- on a proven big man.

The Golden State Warriors of the past few seasons have provided a blueprint of sorts here, using a platoon of role players at center. JaVale McGee revived his career by catching lobs and blocking shots on a superteam. David West got two rings and more wide-open looks than ever before. Kevon Looney slowly developed into a coveted free agent that is surely out of the Celtics' -- and maybe the Warriors' -- price range. Boston does not have money on its side, but it can offer a significant role, exposure and a chance to go deep in the playoffs. 

Ainge will have options. I doubt DeMarcus Cousins wants to take the room exception again, but crazier things have happened and I have no idea what his market will look like. DeAndre Jordan can probably get more money elsewhere, too. Robin Lopez, a less exciting name, seems like a realistic target, and he would bring defense and professionalism. Taj Gibson and Joakim Noah make some sense, even if Celtics uniforms would look super weird on them. Dewayne Dedmon's shooting and shot-blocking will probably be too expensive, but maybe Maxi Kleber's won't be. Boston would be smart to look at Ed Davis, Noah Vonleh and Nerlens Noel. Enes Kanter showed toughness in the playoffs and it looks like this roster could use his rebounding. Willie Cauley-Stein and Luke Kornet are intriguing for completely different reasons.

If I were Ainge, I'd go after Lopez because I'd be looking for someone who could credibly guard Joel Embiid in a seven-game series. He would also immediately become one of Stevens' favorite players, thanks to his ability to be a high-post passer and screen-setter in Boston's offensive system. Whatever direction the Celtics go, though, they will not be asking anybody to replace the particular genius of Horford, a five-time All-Star who also functions as a glue guy. Just doing the glue-guy stuff is enough.