The Bundesliga side snatched victory in Group G thanks to an Eric Maxim Choupo-Moting spot-kick three minutes into stoppage time after Jonathan Silva had been wrongly penalised for handball.
Television replays showed that Huntelaar's header hit Silva in the face, but referee Sergey Karasev - who had earlier sent off Sporting defender Mauricio - pointed to the penalty spot.
"Today we were very lucky," said Huntelaar. "We were leading 3-1 with 11 players against 10 but then we gave it away. You don't normally win matches like this."
Defender Howedes echoed those thoughts when adding: "Only the three points count but, to be honest, it was a lot of luck.
"Seconds before the end it didn't look like this would be a great evening, but we never gave up."
