Monreal was one of the first to acknowledge Aubameyang’s starring role in the 4-2 victory, who also netted in the closing stages of the first leg at the Emirates Stadium.
“We are so proud of him because he’s scored three goals in a semi-final,” the full-back told Arsenal.com.
“He’s helped us a lot, but it’s not only him, it’s every player. He scored a hat-trick, so we are all really happy for him. We needed him and we needed Laca (Alexandre Lacazette).”
After failing to finish in the Premier League’s top four for only the fifth time in the last 25 seasons, Monreal admitted a Champions League place next term, via victory in final on May 29, remains a top priority.
And after reaching their first European final since 2006, the 33-year-old Spaniard has set his sights on a double celebration in Baku’s Olympic Stadium.
“Our target is to play in the Champions League next season,” he said. “Unfortunately we couldn’t finish in the Premier League top four, but now we have a good chance.
“I can’t remember the last time we played in a European final - 2006 against Barcelona? Now we have a good opportunity to finish the season with a trophy and play in the Champions League next season.”
Despite trailing 3-1 from the first leg in London, Valencia gave Unai Emery’s side an early scare at Mestalla with an 11th-minute goal from French forward Kevin Gameiro.
But any thoughts of a Tottenham-esque comeback were quickly dispelled by Aubameyang’s rapid response just six minutes later – a goal that Monreal admits helped to quieten down the vociferous locals.
“I’ve played here so many times and I know the fans,” he said. “They are one of the best sets of fans in Spain.
“They push a lot and made it hard for us in the beginning. But after 10 or 15 minutes when the game calmed down, we started to play our game, and I think we were the better team from then on.”