The team is also considering cornerback Aaron Ross day to day with a left quad contusion.
Boley injured his hamstring late in the second quarter and did not return. Boley is the lone every-down linebacker for the Giants and the player who relays the defensive calls into the huddle. He has been an instrumental part of the defense.
Defensive end Justin Tuck said teammates describe Boley as the one player the defense can't afford to lose because of his responsibilities and experience at the position.
"Everybody is important," Coughlin said when asked about Tuck's statement. "I don't agree with his statement necessarily. Michael is very important to us, he is our middle 'backer, he communicates very, very well. We want to get him back as fast as we possibly can."
"Someone now is going to have to step up if he can't go and perform the duties that he had to help us win the game," Coughlin added.
Safety Kenny Phillips said the Giants lose an extension of defensive coordinator Perry Fewell on the field if Boley is unable to play.
"He's basically the voice of the defense," Phillips said. "He gets the D-line lined up, he makes a lot of the calls. When he is on the field, that gives Perry opportunities to make a lot of different calls and put a lot on his shoulder. He is a playmaker."
"Him going down was definitely big for us," Phillips added. "We had to throw some young guys in a situation that they weren't necessarily ready for but in the end they played pretty good and they will learn from the game we just played."
The Giants had to use rookies Greg Jones and Spencer Paysinger to fill Boley's role against the 49ers. Jones, a run-stopping middle linebacker, came in on running downs and Paysinger came in on passing situations.
Jones failed to cover Vernon Davis on the tight end's 31-yard catch-and-run go-ahead touchdown in the Niners' 27-20 win.
Coughlin says his rookie linebackers will be able to improve on their play with a full week of practice if Boley cannot play against the Eagles this Sunday.
"The guys are going to have an entire week of practicing at whatever spot it is and how we determine it be played," Coughlin said. "The practice week is the important thing."
The Giants also will wait to see if running back Ahmad Bradshaw will be able to return. The running back has missed the last two games with a fractured bone in his foot.
"We'll see," Coughlin said when asked if Bradshaw might practice this week. "There is no sense speculating. He is going to have to go out and practice. He certainly has had a couple of good solid weeks of rest and hopefully he will be able to do some things. Probably won't know until we get him out there."
Ohm Youngmisuk covers the Giants for ESPNNewYork.com.