In normal circumstances, Gregory would probably be no more inclined to call in Eileen Drewery than Ian Dury. However, the prospect of Merson's mysterious ailment keeping him out of Saturday's visit of Manchester United, and perhaps the games with Chelsea and Arsenal which follow, might persuade the Villa manager to consider even the quirkiest of cures.
The pounds 6.75m signing withdrew in acute discomfort during the half-time break at the City Ground. The fact that Villa then clawed back a 2-0 lead which did not flatter Nottingham Forest might suggest that the Premiership leaders can cope comfortably without Merson, but Gregory is only too aware of his importance.
As the only member of Villa's squad with a championship medal, Merson brings precious experience to the cause. He had been their one outstanding performer in the lashing by Liverpool, although Gregory revealed that the injury troubled him so much before the game at Southampton a week earlier that he slept on wooden shelves laid on the floor.
"Mobility is vital in the job Merse has been doing and he was struggling out there," Gregory said. "He could be out for a week or a month, who knows. We haven't been able to find out what it is, whether it's a muscle or a bone or whatever."
The former Arsenal man himself admitted: "I was no use to myself or the team, and tactically the switch needed to be made anyway."
Gregory duly abandoned the role Merson has filled since the arrival of Dion Dublin, as a third attacker floating between the middle and the front, reverting to the 3-5-2 formation with which Villa secured their early success.
Whether or not the back pains relent, the experiment is likely to go on the back burner. After conceding only five goals in the first 13 competitive games, Villa had suddenly haemorrhaged 16 in five and a half.
"I always knew three forwards was a risk," Gregory conceded. "Five in midfield protects the back three a lot better. I was pleased to keep a clean sheet in the second half."
Relieved, too, for Villa were less than half an hour from the first League away defeat of his nine-month reign when Forest squandered the chance to put the outcome beyond reasonable doubt at 3-1. Dougie Freedman, otherwise a revelation alongside Pierre Van Hooijdonk, shot wide when scoring or passing to the Dutchman looked easier.
When Forest failed to clear the ensuing goal-kick, Julian Joachim's raised boot beat Dave Beasant's hands to the ball to equalise. The diminutive striker had already halved the arrears with an equally dubious goal as Dublin impeded Craig Armstrong.
Despite Gregory's concern that Joachim plays "with the heart and not the head", the probable indisposition of Merson and Stan Collymore's suspension mean he is almost certain to face United.
The spirit and style with which Forest started should encourage the belief that relegation is not inevitable. The central midfield trio exploited their numerical advantage impressively. They broke into scoring positions, as Chris Bart-Williams did to stunning effect, and maintained a good service to the strikers, one of whom, Freedman, doubled the advantage.
Their failure to finish off Villa owed as much to a timidity born of a winless run stretching back to August as to Gregory's makeover. Dave Bassett bemoaned their luck, and though he was doubtless grateful for Dublin's dreadful miss at the death, there were plenty of pluses, not least the form and commitment of Van Hooijdonk.
Gregory even described them as "like the Forest of old", detecting a resemblance between the way Bart-Williams, Nigel Quashie and Scot Gemmill initially pulled Villa apart and the slick-passing Brian Clough sides he once played against.
Bassett repaid the compliment, saying he saw "no reason" why Villa should not still be top come the end of the season. With the quality of Merson strained, being there at the end of this week may be an achievement in itself.
Goals: Bart-Williams (32) 1-0; Freedman (44) 2-0; Joachim (59) 2-1; Joachim (63) 2-2.
Nottingham Forest (3-5-2): Beasant; Hjelde, Chettle, Armstrong; Stone, Gemmill (Johnson, 77), Quashie, Bart-Williams, Bonalair; Freedman (Darcheville, 85), Van Hooijdonk. Substitutes not used: Edwards, Harewood, Crossley (gk).
Aston Villa (3-4-1-2): Oakes; Ehiogu, Southgate, Barry; Watson, Hendrie, Taylor, Wright; Merson (Thompson, h-t); Joachim, Dublin. Substitutes not used: Grayson, Scimeca, Vassell, Rachel (gk).
Referee: G Willard (Worthing).
Bookings: Forest: Gemmill, Van Hooijdonk, Bart-Williams, Quashie. Villa: Southgate, Hendrie.
Man of the match: Bart-Williams.
Attendance: 25,753.Reuse content