Gay, traded from Memphis to Toronto last season, is in his eighth season and has averaged 18.0 points, 5.9 rebounds and 2.1 assists in his career.
"Rudy is a prince of a guy. He's an athletic, dynamic wing player, he gets to the basket at will and can shoot the ball and handle the ball," Raptors coach Dwane Casey said.
While the Kings wait for their big acquisition to arrive, they'll continue to rely on McLemore. The seventh pick in this year's draft has seen his playing time and production rise as the season has progressed. He logged a season-high 38 minutes Saturday at Utah and hit a 3-pointer with 3.2 seconds remaining to force overtime.
Sacramento (5-13) went on to win 112-102, and McLemore finished with 15 points and nine rebounds. DeMarcus Cousins led the way with 28 points and Isaiah Thomas scored 23 of his 26 after halftime.
"Isaiah was telling me after the huddle that I was going to hit a big shot," McLemore said. "And I thought I was going to make it even though I had missed a couple of 3s earlier."
Thomas called McLemore's clutch basket, "the biggest shot of his NBA career so far."
The Kings need his development to continue as they rank 24th in the NBA with a 43.0 percent field-goal percentage. McLemore is second among rookies in points per game at 10.1, but he's averaged 13.7 over the last six games. He scored a career-high 20 on Dec. 6 against the Los Angeles Lakers.
"We've been waiting on one of those from Ben," Cousins said of McLemore's clutch shooting against the Jazz.
The Mavericks (13-8) have dominated the Kings in recent years, going 23-3 against them since April 4, 2006 -- including victories in the past five meetings.
Dallas is coming off a dramatic 108-106 victory over Western Conference-leading Portland on Saturday. Monta Ellis sank a 21-foot jumper as time expired to give the Mavs their third consecutive victory.
Dirk Nowitzki has played well over the last four games, averaging 24.3 points on 53.4 percent shooting. Against Portland, he scored 28 to go with seven assists and six rebounds.
Even with Ellis leading the team in scoring at 21.6 points per game, Nowitzki remains the catalyst on offense for the Mavericks.
"We were throwing it to (Dirk) every time," coach Rick Carlisle said of his team's strategy against Portland. "You know, he's going to cause something to happen, something good, and he's going to make it tough on them, so we've got to get the ball in his hands."
The win over the Trail Blazers was the second on a four-game road trip for Dallas, which also faces Golden State before returning home next Saturday.
"Every win is huge, every win you can get is huge," Carlisle said. "We hadn't been playing great on the road this year. Our hope is that we can build some chemistry, build some togetherness out here, which isn't easy.
(Portland) is a hard place to play. Sacramento is hard to play, Golden State is hard to play. So, we have to be really together and this is a positive step in the right direction in a win."