Hearts defender Darren Barr is definitely out of Saturday's match with Ross County at Tynecastle (kick-off 12pm) because of an ankle injury.
The centre-back missed last week's 2-0 defeat by Aberdeen and he will not play for at least two more weeks.
Manager Gary Locke has better news regarding full-back Jamie Hamill, who is available for the first time in 11 months following a knee operation.
Ross County team news to follow ...
Freddie Sears hopes to return for Colchester.
The eight-goal striker, United's leading scorer this season, has missed the last six games with a knee injury but returned to full training on Thursday and, should he suffer no ill-effects, will be back in the fold to face the O's.
Left-back Bradley Garmston overcame a knee injury sustained on Good Friday to take his place on the bench for Monday's 1-1 draw at Oldham and he will be pushing for a starting berth this time around.
George Porter serves the final game of his three-match suspension while defender Tom Eastman is also expected to miss out once more due to injury.
The U's remain just three points above the relegation zone with five games to go.
Leyton Orient will have a makeshift defence when they face the U's.
Scott Cuthbert is out for the season with a fractured metatarsal and fellow centre-half Mathieu Baudry suffered a recurrence of his hip injury against Bury on Monday.
Baudry was replaced by Elliot Omozusi, who is usually a right-back, but he had to go off in the second half with a shoulder injury.
That meant left-back Gary Sawyer finished the game alongside skipper Nathan Clarke in the centre, with utility-man Leon McSweeney filling in on the left.
Further up the field, boss Russell Slade has plenty of options with the likes of Martin Rowlands and Kevin Lisbie pushing for recalls.
Lisbie and fellow striker David Mooney will be hoping to start against their former club.
Midfielder Grimes has been captaining the club's Under-18s this season while goalkeeper Pym was called into the first-team squad to deputise in February when Artur Krysiak missed a match through injury.
The players in the second year of the club's Academy were given the news of their deals on Thursday, with right-back Sam Brown also handed a short-term deal.
Centre-backs Irvine Densu and Kamarl Duncan were not given professional contracts.
"Everyone at Exeter City Football Club would like to extend their utmost gratitude to all five players for their hard work and dedication during their time with the Academy," a club statement said.
"The club will continue to support Irvine and Kamarl beyond their time with Exeter City, and wish them the very best for their future careers in football."
