Sanchez struck after just four minutes of the FA Cup final at Wembley, when he appeared to handle the ball as he blocked N’Golo Kante’s clearance.
But he then ran through to score with teammate Aaron Ramsey in an offside position.
Referee Anthony Taylor gave the goal after lengthy consultation with assistant referee Gary Beswick, who had flagged for offside – but Chelsea were left fuming and went on to lose 2-1.
“That offside rule is a crazy rule,” said Cahill.
Gary Cahill was left fuming over the decision not to flag Aaron Ramsey for offside
Chelsea players protested over the decision to let the goal stand
“You can look to go to the ball and veer off and then not be ruled offside. It is the maddest rule I have ever seen.
“If he [Ramsey] is not there, then maybe our goalkeeper Thibaut Courtois comes out and grabs the ball.
“The handball decision is the most annoying because if that had been given it would not even get to the offside decision.
“If he [Sanchez] gets the ball and has his hands in a natural position down by his side, I understand that. I understand it is difficult when the ball ricochets and it is not your intention to touch it.
“But when you have both hands above your face, you are not telling me that is a natural position.
“It was incredible. I spoke to the referee at half-time and he was adamant Sanchez kneed the ball through. We saw it differently. We were very unlucky.”
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