Welbeck believes that the forward's finishes were a consequence of the high-pressing gameplan implemented by Gunners manager Arsene Wenger.
"The boss told us before the game to press their back four and try to force mistakes. The first goal came from that, so it was something that worked quite well today," Welbeck told Arsenal's official website.
"It's a pleasure to play with Alexis. He's persistent, he keeps going and they are [the attributes of] somebody I like to play alongside.
"It's the same with all the other players in the team. I'm really getting to know the players much better now and hopefully now we can go on a nice run of winning games."
Sanchez has now scored eight goals since joining Arsenal from Barcelona during the summer.