Plenty of familiar names have now changed teams or have come out of retirement to join playoff-bound clubs. Sam Cassell and P.J. Brown became Boston Celtics. Theo Ratliff signed with Detroit Pistons. Tyronn Lue and former Nets player Jamaal Magloire became Dallas Mavericks.

For the most part, these are veterans at the tail end of their prime (and that’s being very generous in Magloire’s case). They are the last chapter of personnel movement this season. Typically, after the trade deadline, losing teams buy out a few of their veterans with contracts that expire at season’s end, freeing them to sign on with a contender. The losing team is usually currying favor with the player’s agent (who might also represent someone on the losing team’s summer wish list). And the player gets to finish out the year with the possibility of making an impact in the playoff race or even in postseason. Every year, some marginal player, such as Tim Thomas, Vladimir Radmonovic, or yes (go ahead and groan, Knicks fans) Jerome James, has a good week or two in the glare of the playoff spotlight and brokers that into a much more lucrative contract than his track record warrants.

How does a spare part on a losing team such as the Timberwolves (Ratliff’s former club), or the Kings (Lue’s former team) find a role on a team heading for the playoffs? Their impact likely won’t make it into a highlight clip, but rather, they will play key reserve roles that will enable their new teams to gear up for the battles that lie ahead in late April and beyond.

Guard Sam Cassell was the most anticipated of these signings. He and Boston forward Kevin Garnett played together on the 2003–04 Timberwolves, a team that reached the Western Conference Finals. In addition, Boston’s most obvious weakness has been their lack of a backup point guard behind starter Rajon Rondo. Rondo, a second-year player, has had a superb season, and the team hasn’t suffered in his absence, winning three of the four games that he missed. Still, if you can add a veteran point guard to aid your playoff run, then you will usually do it. Cassell is no longer much of a three-point gunner, but he’s a smart player who should fit right into the Celtics’ system. His presence will enable them to rest Rondo more down the stretch, and he may provide a boost in their first-and second-round series. (Let’s be fair though: Boston coach Doc Rivers and general manager Danny Ainge could suit up for Boston’s first-round match-up without hurting the team’s chances much. That series figures to be one of the biggest mismatches in NBA history.) The key will be how well Cassell plays in the conference finals, especially if the opponent is Detroit. The Detroit backcourt is bigger, stronger, and more athletic. If the Celtics and Pistons meet in the third round, Boston’s backcourt will still be their most vulnerable spot.

Boston also brought P.J. Brown out of semi-retirement. The 39-year-old pivotman has two roles. One will be to keep former Nets player Brian Scalabrine nailed to the bench, and he’s insurance against rookie forward Glen “Big Baby” Davis getting into foul trouble during a playoff game. Brown can still sink medium-range jumpers, and he’s grabbed 10 rebounds in 23 minutes of action so far in Celtics green.

Ratliff probably didn’t anticipate leaving Minnesota and starting right away for the Pistons, but he’s made the opening tip twice already. Rasheed Wallace is on the shelf with an ankle injury, and coach Flip Saunders is more comfortable bringing third-year forward Jason Maxiell off the bench. So Ratliff, a pivotman who was an excellent shot blocker in his prime, fills a need immediately for the Pistons. If he’s able to contribute consistently (injuries have plagued the 34-year-old Ratliff for the last three seasons), then he’s insurance against opposing teams who deploy big lineups on the perimeter-oriented Pistons in the deeper rounds of the playoffs.

Why did the Dallas Mavericks outbid the Phoenix Suns for Sacramento castoff Lue? The answer is Spurs guard Tony Parker: When the Mavericks traded for Jason Kidd, they gave up Devin Harris, a player who was excellent defensively against their rival’s point guard. Lue, a 30-year-old guard, has stuck around the league for 10 years due to his defensive tenacity. Kidd is still a top defender, but he now struggles against smaller quicker guards; that just became Lue’s beat.

The bevy of talent that the Mavericks gave up to get Kidd also explains their signing of Magloire. Parting with solid backup pivotman DeSagana Diop left the Mavs thin in the paint. I’m not convinced that Magloire is the answer but he may have been the only available choice.

The most important late season veteran addition may happen in a couple of weeks when former Spurs swingman Brent Barry is free to rejoin the fold in San Antonio. He was traded to Seattle in mid-February and was immediately waived by the Supersonics. He must wait a month to rejoin his former club (he could have signed with one of the other 28 teams right away; so it’s suspected that he’s heading back to Texas). Barry played a key role with the Spurs as a three-point sharpshooter. When he dons a San Antonio jersey again, they may become the favorite to repeat.

mjohnson@nysun.com