The junior led the Terps in scoring last season, averaging 15.1 points per game.
Smart played in 22 games as a freshman, tallying 30 points.
Turgeon's contract will pay $17.5 million over five years.
Russell averaged 14.7 points, 4.5 rebounds and 4.5 assists with Rhode Island this season.
Wahab fills a desperate need for the Terps in the low post.
Marial averaged 1.3 points and 1.3 rebounds while playing under six minutes per game this season.
Quinerly scored 14 points and notched 11 assists Monday night.
The Crimson Tide hit 16 threes to dash the Terps' Sweet 16 hopes.
“Our talent level’s not where it’s been. But our toughness is at an all-time high.”
The Terps held the Huskies to 32.3 percent shooting.