The Spain international, 27, was booked in the 24th minute for encroaching on a free-kick and was handed his marching orders just two minutes later for kicking out at Darren Fletcher in a poorly timed tackle.
Salomon Rondon scored the only goal of the game - his fourth in his last six Premier League games - and former defender-turned-pundit Carragher was unimpressed with both United's defending and Mata's first-half meltdown.
READ MORE | Mata takes a hammering after Manchester United red card
He told Sky Sports : "It maybe wasn't a great decision for [Chris] Smalling to step out but [Matteo] Darmian has his back to the ball. He should fill in as Smalling goes out. He's so obsessed with (Stephane) Sessegnon. He should clear, and maybe Daley Blind should be tighter to the ball, but he's not watching the ball!
"It's stupid [from Mata] and you don't normally expect that from him. I can't think what he thinks. He's always going to get a yellow card [for blocking the quick free-kick]. It's so unlike him.
"He knows with the second one. He's trying to pull his leg away as he's halfway through it. You can't help but like Juan Mata."