He left Sunday's Hall of Fame game against the Cincinnati Bengals with what was described as some sort of leg injury. At the time, he was the game's leading receiver with four receptions for 60 yards.
As it turns out, it's a very serious injury.
According to Tim McMahon of ESPNDallas.com, Phillips tore his ACL and will miss the 2010 season. An MRI confirmed the injury on Monday morning.
"It's disappointing because he was having such a great camp and such a great game," tight ends coach John Garrett said after Sunday night's preseason win. "But I know one thing: He's got great resolve. He's got great perseverance. If there's anybody going to come back even stronger than he was before, it'll be John Phillips."
SB Nation's Blogging The Boys has video highlights of Phillips' night against the Bengals including the play in which he was injured.