If you believe Williams, Friday night's game at the TD Garden holds no more importance to him than Wednesday's tilt with the Jazz. He swears he has nothing to prove against a team that gave up on him in less than a season and a half.
But Williams has also never had the opportunity to really make a statement against the Hawks. In those four previous meetings -- three with Sacramento and one with Minnesota -- Williams never logged more than nine minutes of play, totaling 12 points and 4 rebounds in 25 total minutes of action.
Williams is averaging 16.4 minutes per game in Boston, where he's carved out a role as a dependable, high-energy big man off the bench. Sure, his averages of 6.8 points and 5.2 rebounds still don't befit that of a former No. 5 overall pick, but Williams isn't trying to live up to those expectations any more.
The other night, Celtics coach Doc Rivers ran down the Celtics' offseason checklist, which included priority No. 1 Rasheed Wallace, and priority No. 2B Marquis Daniels (2A would have been Grant Hill, who instead re-signed with the Phoenix Suns). You get the feeling that signing Williams might have ranked somewhere below finding the next Lucky the Leprechaun on the organization's priority list.
That's not to belittle Williams, but the Celtics were anticipating bringing back restricted free agent Glen Davis, who had performed so admirably in a starting role when Kevin Garnett was injured last season. Between Wallace and Davis, there weren't a lot of minutes available in the frontcourt.
Williams arrived to fill the kind of role that Patrick O'Bryant was brought in for last year. O'Bryant, ironically, was another disappointment from that 2006 draft, never quite living up to his hype as the ninth overall selection.
While injuries have helped open doors for Williams, he's far exceeded what O'Bryant provided (1.5 points, 1.3 rebounds, 4.2 minutes per game). Just ask his teammates.
"The shocker here is probably Shelden Williams," Garnett said when asked about the bench after Wednesday's win. "I don't think everybody anticipated his work ethic and how he's able to keep rebounding and his production within the small minutes that he plays. He's rebounding, he's keeping balls alive, he's perfect for this team. He's that live wire that we need, especially with Glen being out; he's come in and filled the void that was lost for a second. He's just high energy."
Rivers has stressed that Williams is still finding his way in the Celtics' system. But he's often repeated that, "every day is a better day for Shelden with us. We just keep selling him his role."
Williams never quite knew his role in Atlanta. Earlier this season, he voiced frustration in never being able to find his groove with the Hawks. Just when he seemed to finally prove himself at the end of his rookie campaign, the Hawks drafted big man Al Horford, which relegated Williams to the bench.
"When I did get a chance to play [in Atlanta] ... I was averaging a double-double ... and earned the rookie of the month honor [for April]," Williams noted earlier this year. "I thought things were changing. I showed when I got a lot of minutes, I can be effective at this level. But they made changes, other people got drafted."
By February of 2008, Williams had been shipped to Sacramento in a trade for Mike Bibby. A year later, he got dealt to Minnesota. Boston marks his fourth stop in four years.
Now, Atlanta seems like a lifetime ago. Since his time there, he's married WNBA superstar Candace Parker and welcomed their first child, Lailaa Nicole Williams, this past May.
In Boston, he's been given a chance to reinvent himself. No longer is he the fifth overall pick, weighed down by the expectations of his lofty draft status. Now he's simply a cog in the bench of one of the top teams in the NBA and he's overachieving.
Williams is reveling in it all. Earlier this season he joked about how the Celtics' 6-0 start was the longest winning streak he'd been a part of in the NBA.
Should you believe him when he says Friday's game doesn't hold any added importance? No, it seems unlikely that Williams can see guys like Bibby and Horford and not be reminded of his past.
But on Friday the 13th, the man who now wears No. 13 has a chance to exorcise some of those demons from his past.
Chris Forsberg is a roving reporter for ESPNBoston.com. Follow him on Twitter.