The on-loan Saints forward, who was starting only his third game for the League 1 side, is set to undergo a scan today in order to determine the extent of the damage suffered to his knee.
Seager suffered the injury just minutes after netting for Crewe, as they came from two goals down at Spotland to salvage a point.
Seager produced a smart, low finish from Brad Inman’s cutback in the 27th minute to cap what had been a lively start from him, after earlier being denied by a save from Rochdale keeper Josh Lillis.
However, his night ended prematurely when he appeared to twist his knee shortly after his goal.
“It was an up and down night for Ryan,” said Crewe boss Steve Davis. “We were pleased for him to see him score his first professional goal. It was a great move down the right hand side and he pulled off his man to finish Brad Inman’s cut back. That is what he does, he is a good finisher.
“The momentum was with us until Ryan suffered his injury. We are all gutted for him. We just all felt sorry for Ryan because he is a good lad.”
Crewe had found themselves 2-0 down after just six minutes, following Rhys Bennett and Joe Bunney’s efforts, but Marcus Haber pulled one back for the visitors in the 24th minute, before Seager struck shortly afterwards to earn Crewe a point that keeps them 22nd in the table.
Elsewhere in League 1, Sam McQueen came off the bench in the second half for Southend United, as they lost 2-0 away to Bradford City.
McQueen was introduced in the 59th minute, by which time the Bantams were already a goal to the good, following Tony McMahon’s curling, 25-yard free-kick in the first half.
Bradford then sealed the win in the 74th minute, through a James Hanson header, as Southend remained seventh in the table, ahead of their opponents only on goal difference.