Leonard suffered a sprain of his left foot late in the second quarter on a reception and was helped from the field. He did not return and will be further examined when the team returns to training camp.
Phillips, who had four receptions for 60 yards, had his right knee examined after leaving in the first half and did not get back in the game. Afterward, he said he thought he tore something.
Phillips will undergo a magnetic resonance imaging test Monday to determine whether he tore the anterior cruciate ligament in his right knee.
Phillips believes he injured the knee when he landed after catching a back-shoulder throw from Jon Kitna. It was the second of four receptions for Phillips, who left the game after he collapsed while battling with Bengals defensive end Frostee Rucker as he tried to release into a pass route.
The preliminary diagnosis is that Phillips, a sixth-round pick who contributed as a rookie last season, suffered a torn ACL that would be a season-ending injury.
Also injured were Bengals veteran safety Chris Crocker (right ankle) and rookie running back Cordera Eason (right foot); Cowboys receiver-kick returner Titus Ryan (broken left thumb); Dallas tackle Alex Barron (sprained right ankle); and Cowboys tight end Kevin Brock (sprained left ankle).
Eason, an undrafted rookie out of Mississippi, returned for the next series in the fourth quarter, then left for the locker room on a golf cart.
Information from ESPNDallas.com's Tim MacMahon and The Associated Press was used in this report.