Phil Parkinson admitted he named the wrong team after City again came back goalless and empty-handed from another away trip.
The 1-0 loss at Shrewsbury was their sixth in a row on the road, although other results at the bottom went well for them, with Hereford, Macclesfield and Barnet all losing.
With four games left, City remain seven points off the relegation zone with a much better goal difference on the sides in trouble.
But Parkinson felt he slipped up yesterday by keeping faith with the side that had beaten Southend three days earlier.
He said: “I have to look at myself and maybe I should have made a couple of changes.
“I wanted to play the same team just to get that bit of continuity with the threat from the bench, which I felt could have won us the game.
“I just felt I’d go with the side that had done so well on Friday. That was a terrific performance but I think it told on our legs.”
Jermaine Grandison’s first-half goal kept up Shrewsbury’s unbeaten home record.
Nahki Wells, who was subbed by Chris Dagnall at half-time, had chances to hit back and Craig Fagan missed a close-range volley when it looked easier to score.
Parkinson added: “Nahki didn’t pull the trigger quick enough. I thought he looked tired and I had to make some changes.
“Fages was in the six-yard box and you expect that to go in.
“The most disappointing thing was to concede a scrappy goal because we had chances to clear and didn’t do it. It’s frustrating because in the main we coped reasonably well.
“We worked our socks off in the first half but were slightly low in our intensity levels. But I thought we improved immensely in the second when the fresh legs helped us.”
Skipper Michael Flynn, who again started on the left of midfield, was also taken off at the break for Kyel Reid.
Parkinson said: “Reidy took a while to get his second wind but he’s had nearly two and a half weeks when he hasn’t trained.
“Flynny created two goals on Friday and did well. He looked a bit leggy for it but he’s a good player.”
City face the Football Association today to find out their punishment for their part in the Crawley brawl.
The club are not contesting the charge of failing to control their players but Jon McLaughlin, one of the three sent off, will join director of
operations David Baldwin at the Wembley hearing to put their case across.
Parkinson said: “It will be nice to move on from that at last. It’s been hanging over us.”