Berhalter, once of Crystal Palace, chose to quit 1860 Munich to return to the 'States last year.
"I was very pleased with Gregg," Arena said. "We thought he could help and play in this league, and he certainly demonstrated that. I think we needed someone to help stabilize our back line, and he was a player with a lot of experience who was fit enough and healthy enough to endure an MLS season.
"And certainly Gregg did that."
Now in the veteran stage, Berhalter says retirement has not crossed his mind.
He told mlsnet.com: "I really enjoy being out on the field and I feel good.
"I think the obvious step would be some type of coaching career; that's not written in stone but it's an obvious progression for me.
"But right now I'm really enjoying my playing time and just trying to stay fit and help the team."