With only Nigel Winterburn on the serious casualty list at the moment, injuries are thin on the ground, though both Joe Cole and Fredi Kanoute - who will not play again until the Sunderland game - are suspended for the crucial trip to West Bromwich Albion next week.
"We can't afford to have any injuries for what is the period of the run in with 11 games to go; the vital factor in our survival will be keeping everybody fit, which then creates competition for places," says Glenn.
"If you have got anything about you as a person or as a footballer competition keeps you on your toes - and we now have that in most positions.
"It is a vital ingredient - you want to be keeping a consistent selection of 11 players and find a winning formula with that and very few changes, but those player who are playing the games know they can't afford to play poorly because they know there are players willing to come and take their place.
"Teams that do well don't have many injuries and basically work with 12 or 13 players for most of the season.
"They have enough players chomping at the bit to get a game, with players in the team knowing they can't afford to have two bad games on the trot because if they do they will be out of the team.
"Southampton have done brilliantly this year and I think Gordon Strachan has said recently himself he hasn't had to make too many changes because the team has stayed fit all year, week in, week out."