Bellerin believes Welbeck deserves to be back to his best.
He said: "He's a player who, even when he doesn't score, always does a great job for the whole team with his movement and runs in behind.
"All the work that he's been doing this season has paid off because he's done very well these past few games. I'm really, really happy for him to find the back of the net."
Bellerin added: "I think we're one of the biggest teams in the competition right now. The Europa League has one of the best groups of teams that it's had in a while this year, so it's going to be really hard. Of course, we know we have the potential to make it to the top."