Crawley closed the gap on the top six to four points with three games to go after goals from Billy Clarke and Connor Essam gave them maximum points on a heavy pitch at the Broadfield Stadium.
Pressley believed conditions had deteriorated so badly that a halt should have been made in the second half.
He said: "I don't think the game should have finished. I know it's very easy to say that when you've lost the game, but the fourth official came to me at the 60th minute and asked my opinion and at that time the surface was unplayable.
"The referee's reason for continuing was that the penalty areas were ok, but you've got to remember there's another 80 per cent of the pitch to consider. It was unplayable.
"It made life treacherous for us and difficult in terms of trying to pass the ball, which is what we want to do as a football club."
Coventry withdrew their appeal earlier this week against a 10-point deduction for entering administration meaning the club cannot be promoted or relegated from League One this season.
And Pressley admits that galvanising his players through the remaining games will be a challenge.
He added: "It's a difficult period for us because there is a lot of uncertainty and a number of issues at the club. A number of players are coming towards the end of their contracts.
"But we need to maintain focus until the end of the season. I told the team before the game that, although we were giving a number of young players an opportunity, it was still about winning the game."