Decker said the early indication is that it "might be" a posterior cruciate ligament sprain, based on a battery of postgame tests. He said his knee "held up fine" during the tests, but doctors want an MRI for confirmation.
Even if it doesn't require surgery, Decker likely will miss time.
"I'm going to be smart about it this time," said Decker, who played through a serious hamstring injury last season. "I'm not going to rush myself. Obviously, I want to be out there as soon as possible, but we're going to take the proper steps."
The timing is lousy, as Decker is coming off a huge game. He caught eight passes for 97 yards and a touchdown, all in the first half -- the most prolific first half of his career.
He left in the fourth quarter after a Colts defender landed on him following a long incompletion.
"I landed goofy," he said.