Richards, MVP of the playoffs when the Lightning won the Stanley Cup in 2004, was Tampa Bay's fourth-leading scorer with 51 points (18 goals, 33 assists) in 62 games. He will be third on the Stars' scoring list, six points ahead of Mike Modano.
Tampa Bay is last in the Eastern Conference and looking to clear salary cap space two years after signing Richards to a five-year contract that averages $7.8 million per season.
"I've played on every team in my life since I was 14 with [Lecavalier]. He's my best friend," Richards said. "It goes without saying, that part was tough. But I kind of got past that mentally now. That's why I'm so excited."
Richards, who waived his no-trade clause, said Dallas topped the list of teams he would consider joining.
The appeal for the Stars was adding a proven playoff scorer in their effort to get out of the first round for the first time since 2003. In the 2004 playoffs, Richards set an NHL record with seven game-winning goals and led the league with 26 points in 23 games.
Entering Tuesday's game at St. Louis, Dallas had won 11 of 13 games to solidify the No. 2 seed in the Western Conference behind Detroit. Catching the Red Wings is unlikely but not impossible.
"I have played in the playoffs the last four years. I can't wait to get back in them," Richards said. "I will keep playing the way I always have in the playoffs, and been successful, and we'll see what happens."
Besides switching teams, Smith and Holmqvist are trading roles as well.
Smith will probably be the starter for Tampa Bay after challenging Marty Turco for that role in Dallas earlier this season. Ultimately, Smith made 21 starts to 47 for Turco, who had eight of the Stars' past 11 wins before Tuesday. Smith was 12-9 with a 2.46 goals-against average in Dallas.
Holmqvist was 20-16 with a 3.01 goals-against average in 45 games as Tampa Bay's starter. He will back up Turco.
The Stars haven't been hurting for offense. They've scored at least four goals six times during their current 11-2 run, and they rank seventh in the league at 2.89 goals per game.
By adding Richards, the Stars picked up almost as many points as they gave up in Jokinen (28 points in 52 games) and Halpern (24 points in 64 games).
Dallas also is adding a player considered one of the league's rising stars just two years ago. Richards followed his Stanley Cup MVP season with a career-high 91 points in 2005-06, the first season after the lockout.
He should add to the scoring depth at center for Dallas. Mike Ribeiro leads the Stars with 71 points (26 goals, 45 assists). Modano has 17 goals and 28 assists.