The first part of the Celtics’ roster building is complete. With Jeff Green back in the fold, they now have 10 players committed to contracts for next season with three more on minimum deals that are not fully guaranteed in E’Twaun Moore, Sean Williams and second-round pick Kris Joseph. The next step will require some creativity.

Deals can’t be officially signed until Wednesday, so it’s a bit of a guessing game to see where the Celtics stand in relation to the salary cap and the all-important luxury tax apron. What we can say with certainty is that they will be over the cap -- likely $58 million -- and by committing the full mid-level exception to guard Jason Terry they must stay under the tax apron, estimated to be $74.3 million. The league’s audit will determine those numbers and will be completed early this week.

That leaves team president Danny Ainge with few options to fill out the rest of the roster and a major priority to find another guard in the wake of Ray Allen’s departure to Miami and Avery Bradley’s surgery on Tuesday on his right shoulder. Bradley already had surgery on his left shoulder, which caused him to miss the remainder of the playoffs, and he could miss all of training camp and the beginning of next season.

With the mid-level gone to Terry they are down to the bi-annual exception, which is a deal that starts at $1.9 million and could be for up two years. That won’t be nearly enough to lure players like O.J. Mayo, Lou Williams or Courtney Lee, but they can also explore the sign-and-trade route and Lee has emerged as a prime target.

Coach Doc Rivers met with the free agent guard in Orlando, who is an excellent defender and 3-point shooter. Lee particularly excels at shooting the corner 3-pointer and is an expert cutter off the ball, all of which would make him an ideal replacement for Bradley. The Rockets rescinded their qualifying offer to Lee making him an unrestricted free agent, and they are said to be interested in sign-and-trade offers.

The Celtics don’t have much to offer – draft picks can not be traded for 30 days after signing their contracts -- but they do have Moore and Williams on nonguaranteed deals, as well as last year’s first-round pick, JaJuan Johnson. They also have what should be a valuable second-round pick that in 2013 that belonged to the Bobcats and was received from Oklahoma City via the Green trade. Future draft picks are worth zero dollars in trade economics but can be used as sweeteners. Finally, they could also bundle one of their other remaining free agents in a deal if those players were amenable.

By staying under the luxury tax, the Celtics have more flexibility on trades and would be able to bring back as much as 150 percent of their outgoing value. For example, if they came up with $2.7 million in outgoing contracts, they could work out a deal with someone like Lee that would start at over $4 million annually and the Rockets would get a nice little $1.3 million trade exception out of the deal.

Long story short, it can be done but there will be a competitive market for players like Lee and it would be in the Celtics’ best interest to try and get a deal with him as that market will only intensify.

Internally, the Celtics could re-sign Mickel Pietrus, but as a non-Bird free agent who played for the veteran minimum last season, the most they can offer is the bi-annual exception. The two sides have talked but no offer has been made. They could also bring back Keyon Dooling, but as an Early Bird free agent they would have to offer a two-year deal. (They could also renounce his rights and bring him back on a minimum deal.)

Then there’s Moore, who showed flashes of being an NBA-caliber combo guard, but his 331 minutes is not enough of a track record to simply hand him the job. This is an important summer for the Purdue product to show that he can be part of the team’s future. The second-year of his contract becomes guaranteed if he’s not waived by the end of their summer league schedule in Las Vegas.

WHAT ABOUT STIEMSMA?

The Celtics have been waiting to see if restricted free agent Greg Stiemsma receives an offer from the Timberwolves, who have been in talks since last weekend. Those talks continued on Saturday and while his agent insists that no offer has been made, the speculation is that it could be for $3 million.

Stiemsma is gone if that happens because the Celtics would have no means to match. As a non-Bird free agent with two years of service time in the league (he actually signed with the Wolves before the last game of the season in 2010), the Celtics can only match up to 120 percent over the veteran minimum, which would be a little more than $1 million.

The Wolves are in the midst of an awkward cap dance of their own as they try to clear space for a four-year, $45 million offer for Nic Batum, so Stiemsma’s offer will have to wait until after that takes care of itself. Restricted free agents can sign offer sheets on July 11 and teams will have three days to match, so this could linger into the weekend.

Without Stiemsma, the Celtics will likely be in the market for another big man but it’s not as dire as some would think. Brandon Bass and Kevin Garnett figure to start up front and with Jeff Green back on board, he’ll add versatility and depth. Behind them sit rookie Jared Sullinger and Fab Melo, as well as Johnson, who, like Moore, is also looking to make a big improvement in his second season.

If the Celtics don’t use their bi-annual exception on a guard, it could be used on a veteran big man. There is interest in having Chris Wilcox return for a second tour, but the Celtics don’t have his Bird rights because they waived him last season after he underwent heart surgery. He could be a decent match for the bi-annual exception.

They also retain Bird rights on Nenad Krstic, who spent last season with CSKA Moscow. Overseas reports that Krstic may not return to Russia, but it’s unclear whether he wants to get back into the NBA. One thing the Celtics can’t do is use Krstic in a sign-and-trade. He’s not eligible because he wasn’t on their roster last season.

No one ever said rebuilding a roster would be easy and while Ainge accomplished almost everything on his to-do list, the last steps will be the toughest.