Phillips hurt the knee during Sunday's 38-35 loss to the Green Bay Packers. The bad news is that it's the same knee that he underwent microfracture surgery on during the 2009 season.
Head coach Tom Coughlin said Phillips was getting tests done Monday.
"I don't know...honestly because you have seen them jump up and run off the field and the next day it is an ACL."
In other news, backup offensive lineman Stacy Andrews will miss the rest of the season.
Andrews was hospitalized Saturday night because of pulmonary embolisms in both lungs.
"It is a very, very serious medical condition," Coughlin said.