The Welsh outfit lost 3-1 away to Benitez's Napoli on Thursday to bow out at the last-32 stage of the Europa League.
Former Liverpool and Chelsea manager Benitez saw enough of Swansea in the goalless first leg at the Liberty Stadium and the return fixture in Italy, however, to be convinced they are heading in a positive direction under interim boss Monk.
Napoli are third in Serie A and missed out on the Champions League knock-out stage on goal difference, while Swansea stand 12th in the Barclays Premier League heading into the weekend. They face Crystal Palace on Sunday.
Benitez said: "They were a very difficult rival for us. They play good football and they are a very good team.
"We have to give them credit because we had to work very hard to progress.
"I'm surprised by Swansea's position in the Premier League standings but they are coming back with a new manager to the level they were before.
"I give credit to Monk, I think he has a great future ahead of him."
Swansea are just four points above third-bottom Sunderland in the Premier League, and the Black Cats, who tackle Manchester City in the Capital One Cup final on Sunday, already have one game in hand.
Monk, who took over from Michael Laudrup on February 4, feels his team can take plenty of positives from their European adventure this season.
"It has been a great journey for the team, for the fans and for the club," Monk said. "The atmosphere has been great in both legs."
Swansea dominated the first leg of the tie but could not make a breakthrough at home. Another solid performance followed in Naples but the Swans fell just short.
"I feel for my players," Monk said. "They did everything I asked of them.
"We had our chances in both ties but I can't hold my players accountable for that.
"It's disappointing but also pleasing to be able to create so many chances against a great side like Napoli and also to do so away from home.
"Napoli have two great goalkeepers and I think that was the key.
"But my players can really hold their heads high and be proud of what we've done.
"The message I told my players after the game was that whatever happens in your careers, make sure that you play with that belief."
Napoli goalkeeper Jose Reina made a stunning save from Wilfried Bony's header to prevent Swansea taking a 2-1 lead midway through the second half on Thursday.
"We knew it was going to be hard," Monk said. "Napoli are a very good side, with very good players and a great coach.
"They were better at certain stages of the game than us so credit to them."
Monk took strength from Swansea's obvious enthusiasm for their task.
"To see that desire to win in my players is good," he said. "With that hunger you will win more games than you will lose.
"We need to take that belief into our league knowing that we have played very well in the two legs against a very good team."
Swansea earned their European place by winning last season's League Cup, and Monk said: "When you get a taste of European football, you want more of it. You want to get back to play in Europe as soon as possible.
"Hopefully going forward as a club we can achieve that."