Before leaving the game for good midway through the third quarter, Ball piled up 16 points and 10 assists, helping the Lakers advance to the final with a 108-98 win. Los Angeles will play the Portland Trail Blazers for the title on Monday.
According to ESPN.com, Ball was available to play late in the game Sunday, but he was held out.
The crowd in Las Vegas to watch Ball and the Lakers on Sunday, ESPN reported, included the team's president of basketball operations, Magic Johnson, plus general manager Rob Pelinka and coach Luke Walton. Assistant coach Jud Buechler is running the summer-league team.
Ball, 19, was the second overall pick in the NBA Draft this year out of UCLA. He has recorded two triple-doubles in the summer league.
Another Lakers first-round rookie, forward Kyle Kuzma, led the team with 24 points Sunday, and guard Matt Thomas scored 20.
Guard Dennis Smith Jr., also a first-round pick this summer, paced the Mavericks with 21 points and six assists.
Forward Jarnell Stokes scored 22 points and grabbed 15 rebounds to power the Trail Blazers to an 87-82 win over the Memphis Grizzlies in the other semifinal. Grizzlies forward Dillon Brooks, a rookie second-round pick, scored a team-high 16 points in the loss.