The Brazilian defender had been an ever present for Chelsea in this season's Champions League but a hamstring injury kept him out of the first leg and he's unlikely to figure in the Nou Camp either.
If Cahill endured a difficult start to life at Stamford Bridge, the England defender is rapidly showing his worth at the heart of Chelsea's defence.
His return to the side has coincided with Chelsea keeping successive clean sheets and his performance against Barcelona was imperious. The 26-year-old had never come up against Lionel Messi before, but acquitted himself with poise and intelligence to help snuff out wave after wave of Barcelona attacks.
And England's management, whoever they may be, should be cheered by the sight of Cahill forming a robust partnership with John Terry. Chelsea have won three and lost none of the five matches they have started together and have conceded just once in those matches. Whether either will end up on the plane to Krakow remains to be seen, but a revitalised Cahill is giving himself every chance.
Elsewhere, if Barcelona are to progress, they will have to deal with Didier Drogba rather better than they did at Stamford Bridge. For all their technical prowess, the Spaniards are very obviously vulnerable in the air, and neither Carles Puyol nor makeshift centre-half Javier Mascherano looked comfortable up against the powerful Ivorian. Pep Guardiola could restore out-of-favour Gerard Pique, who has missed Barcelona's last five matches, to the side.
Further afield, Guardiola has to decide whether to hand recalls to either Cesc Fabregas or Alexis Sanchez, both of whom were dropped for Saturday's Clasico. Sanchez, in particular, would appear to have a strong case. Cristian Tello hardly endeared himself to the Barcelona faithful, spurning a gilt-edged chance early in the second-half. And while Sanchez's goal wasn't exactly a thing of great beauty, he can at least claim to have made an impact. The Chilean can count himself very unlucky should he end up on the bench once more.
Can Barcelona overcome the disappointment of successive defeats to qualify for the final? The Spaniards are [1.29] to win on the night.