Beal underwent an MRI on Monday after experiencing soreness in his lower leg.
Beal, who leads the Wizards (5-8) in scoring with 20.6 points per game and the league in minutes played at 40.2, suffered a stress injury in the same leg that prematurely ended his rookie season.
Porter, selected third overall in the 2013 draft, has been sidelined since the start of training camp with a right hip flexor injury.
Ariza has been nursing a right hamstring strain and missed the team's past five games, while Singleton has yet to play this season due to a broken left foot.
Coach Randy Wittman said that of the three players who returned to practice, only Ariza is expected to play Tuesday night against the Los Angeles Lakers.
Information from The Associated Press was used in this report.