Garner felt his players struggled physically at the County Ground following multiple COVID cases within Swindon's squad, which resulted in an 18-day break between games.
Cobblers will face a similar challenge should Saturday's game go ahead having gone 21 days without a game.
“I was proud of the players tonight," said Garner despite being held by relegation-threatened Stevenage.
“I think considering the number of players who were hit by Covid and the limited training time we’ve had, I thought it was a fantastic effort.
“Some of those players were in bed for five or six days, they were isolating for 10 days, they’ve come in for two days training, and then gone on to play 90 minutes.
“It shows the character of the players and their willingness to fight for this football club and for the group.
“We were off where we would normally be, physically, without any shadow of a doubt. We worked as hard as we could, but it is what it is.
“There will be other clubs in similar positions when they start getting their players back. That game will do a lot of players the world of good.
“We’ve got a very, very quick turnaround now – it’s a strange situation, but it is what it is and we’ll try to do the best we can.”