Southgate had to be dragged kicking and screaming to include Grealish in the first place back last September, remember.
But if the Poland victory showed anything – apart from that some prayer space also needs to be reserved ahead of the Euros for John Stones good days – it was that England need Grealish. Not as a starter but as a match-turner off the bench.
It took 86 minutes for England to bring on a substitute against the Poles. That was Reece James for Phil Foden as Southgate moved to a back five to shore up the defence after Harry Maguire had just given them the lead.
Up until then, with England chasing a goal which stubbornly refused to come, nothing.
It was a substitute – Eder – whose goal won Portugal the Euros against France in extra time five years ago. This time around, with an expanded five permitted per team, bench firepower is likely to be even more important.
The lack of incendiary options at Southgate’s disposal at Wembley on Wednesday night makes the case for Grealish for the Euros unanswerable.
He is a lock picker who can pull a tiring defence to pieces.
His form for Aston Villa before the shin injury which has kept him out of the club’s last six games has been outstanding. For England too he has more than looked the part.
The highlights reel flick which nonplussed Thomas Meunier against Belgium in November was high-class showmanship but with a purpose. It won Grealish and England space. That level of imagination and implementation could make all the difference at the Euros.
His reservation, if he is thinking of Grealish as an impact player rather than a starter, is how a sub tag will sit with an individual who is used to being a leading man rather than a support actor.
They can strike anywhere at inconvenient moments as Grealish has found. But while his six-week absence has no doubt been a personal frustration and sapping for Aston Villa, it may prove a blessing in terms of a summer international tournament.
When others are on their knees after congested domestic seasons Grealish, who is slated to return today for his club against Fulham, should be in good shape for England.
A fresh Grealish trotting onto the pitch, socks round his ankles with half an hour left and a tournament in the balance?
No defence in Europe will want to see that.
My England XI to face Croatia in the opening game of the Euros: Pickford; Alexander-Arnold, Stones, Maguire, Shaw; J Henderson, Foden, Mount; Rashford, Kane, Sterling.
Substitutes: D Henderson, Pope, Chilwell, Mings, Coady, Walker, Rice, Sako, Grealish, Ward-Prowse, Calvert-Lewin, Sancho.