McQuaid slammed headfirst into the boards late in the first period of Monday night's Game 2 overtime win over Philadelphia and lay motionless on the ice for several minutes before skating off with the help of teammates Zdeno Chara and Milan Lucic. He also received help getting to the locker room.
The defenseman was taken to Jefferson Hospital in Philadelphia but flew back to Boston Monday night with the team.
"Everything so far has come out negative," Julien said of testing. "He's a day-to-day player right now."
Should McQuaid be unable to play in Game 3 Wednesday night at TD Garden, it is expected that veteran Shane Hnidy would replace him in the defensive pairings.
The Bruins lead the Eastern Conference semifinals series 2-0.
Brendan Hall is a frequent contributor to ESPNBoston.com.