MIAMI (AP) _ Pat Riley is never quite satisfied, even when his team is winning.

On Friday, the Miami Heat acquired forward Jamal Mashburn from the Dallas Mavericks for three players. It was a typical Riley mid-season trade designed to improve a team that already has the NBA's second-best record.

In exchange for Mashburn, the Mavs' 1993 first-round draft pick, Dallas got forward Kurt Thomas and reserves Sasha Danilovic and Martin Muursepp.

``I said if there was an opportunity for a frontline player who was young and long-term I would consider a trade, and I did,'' Riley, in his second season as coach of the Heat, said. ``Anytime you make a trade there are always risks involved. But to get a starter who averages 21 points a night, it is a risk we have to take in light of the injury to Dan Majerle.

``We felt we needed to shore up the three spot and we gave up good young players to get one very good young player,'' Riley said.

Mashburn, 24, is in his fourth pro season out of Kentucky. In 37 games with the Mavericks this season he is averaging 10.6 points, 3.1 rebounds and 2.5 assists. Over his four seasons in the league, Mashburn is averaging 19.9 points, 4.2 rebounds and 3.3 assists.

Despite Miami's success, Riley had been looking for a strong, powerful forward. Only the defending champion Chicago Bulls (43-6) have a better record than the Heat (38-12), who have won eight straight.

The winning streak currently is the longest in the NBA. The team ranks fourth in defense and has scored 100 points six times in the past eight games. With a patchwork bench, it has overcome injuries to three key players _ Majerle, Thomas and Gary Grant.

But Riley has been eager to improve the Heat's play against the top NBA teams. All the team's losses in January were to playoff-bound teams _ Utah, Seattle, the Los Angeles Lakers, Orlando and New York.

Riley is known for shaking up his team with midseason deals. He traded five players at last year's trading deadline.

New Mavericks general manager Don Nelson is showing the same tendency as he tries to shake some life into a team left dispirited by a 16-30 record and mounting team dissension.

``This is a chance to get three darn good players and change the team,'' Nelson said. ``I think change is good for teams and players; I think it's time that this one changes some.''

The unhappy Mashburn has been rumored to be on the trading block for much of the season but it was thought that plan would be shelved until after the season.

``I think it's just time for a change for Jamal. We wish him the best, I think he's a very fine player. He just didn't seem to be playing up to his best here,'' Nelson said. ``I certainly hope that changes and he become the player he was or wants to be.''

The trade will be something of a homecoming for Thomas, who attended Texas Christian. The 24-year-old former TCU star was averaging 6.3 points and 5.9 rebounds per game before he fractured an ankle Jan. 24 and underwent Feb. 4 surgery.

The former Dallas high school star will be placed on the injured list while he recovers from Feb. 4 surgery on the ankle.

Nelson acknowledged the trade for Thomas was a risk.

``Injuries do happen, and we've taken some risks with Thomas. But we factored that into the equation. We think it's a good gamble,'' he said.