Fernando Rey did not receive an Oscar nomination for portraying Alain Charnier in The French Connection.
Aside from the scenes of him setting up the deal this is mostly a silent performance by Alan Charnier in all of the scenes where Popeye is trying to follow him and keep him in sight. In this part of his performance Fernando Rey is excellent in being the adversary to Hackman's Doyle. In Hackman's performance all the frustrations and the effort of a hard boiled cop, Rey acts as the perfect foil to Hackman's performance as he shows Charnier doing everything to escape Doyle's pursuit while he stays completely calm cool and collected. When the two play the game on the cat and mouse is a great scene but it is made even more memorable by Rey and Hackman's performance. The scene's end is unforgettable as we see the angry Doyle lose Charnier, and Rey's brilliantly smug face as Charnier waves goodbye to Popeye.
Rey is pretty consistent in his performance until the very end of the film when Charnier himself has to deliver the drugs rather then use his patsy friend. Rey is again silent in these scenes and is very good in showing the manner in Charnier change to reflect his grievousness and indicate that handling the deal is clearly the last thing that he ever wanted to do. The best moment comes when the tables have turned with Popeye and Charnier changing places from the subway scene with now Popeye being the one giving the wave. Rey makes the moment extremely satisfying because he shows all the confidence drain right out Charnier face. This is a relatively simple role but one that Fernando Rey handles well with his very assured performance. Rey without much screen time hints at who this man is but more importantly to the film as whole makes Frog one the elusive mystery that you do want to see Popeye catch.