Stenson, who had been playing in the Arizona Fall League, was found dead Wednesday after a night out with friends. Four men have been arrested in connection with Stenson's death.
Police said the robbery began at a Scottsdale nightclub, but the events leading to the discovery of Stenson's body in a street in suburban Chandler were unclear. Stenson's hands were bound during the robbery and there was an apparent struggle in his vehicle, police said.
Stenson was shot more than once while attempting to escape and then was run over, said Detective Robert Krautheim.
David Griffith was arrested without incident on American Indian land east of Phoenix. Griffith, 20, was arrested on a warrant for vehicle theft and held while Chandler police seek extradition.
Upon extradition, Krautheim said additional charges would be sought for Griffith. He declined to elaborate.
Two other men, half brothers, were already being held in connection with the case, one charged with possession of stolen property and the other held on suspicion of robbery, kidnapping and homicide.
Kevin Riddle, 43, was stopped by police while driving Stenson's SUV less than two hours after Stenson's body was found Wednesday, police said.
Reginald Riddle, 19, was booked Thursday on suspicion of homicide, armed robbery and kidnapping. He has not yet been formally charged. According to court documents, Reginald Riddle admitted his involvement during interviews with police.
Their relationship to Griffith was not immediately clear.
A fourth suspect, 32-year-old Robert Lee Maye, was arrested Saturday. He was booked on suspicion of hindering prosecution in the case, police said.
"They are all involved some way or another, and we're trying to figure out how," Krautheim said.
Police also said they are investigating another shooting death nearby for a possible connection. Police found the body of Jarrod Waring, 23, inside a white Buick two days before Stenson was killed. Waring was shot in the head.
Stenson, 25, made his major league debut with the Reds this year, batting .247 with three home runs and 13 RBIs in 37 games.
Funeral services will be Monday in LaGrange, Ga., Stenson's hometown.
By Beth DeFalco