Bertos, who began his professional career with English club Barnsley in 2000 and joined the Phoenix eight years later after a two-season stint with Perth Glory, acknowledged it had been a difficult year for everyone connected with the club.
Making it even more challenging for Bertos was a switch to right fullback after playing most of his career as a wide midfield player.
"It wasn't easy but I actually enjoyed my stint at right-back and I've played a similar role in the national team'' he said. "Football is a team game and if you are asked to play a different position then you just get on with the job.
"I thought I did alright there, but I am more natural going forward and with the way we performed this season I didn't get as many opportunities to do that as I would have liked.
"You watch the top leagues overseas, and also the A-League, and see fullbacks getting forward a lot and that's what I hoped I could do. The way the season went my No 1 role was to defend and I had to learn quickly.
"In the past we have been a hard team to break down defensively but that wasn't the case this year. We have to learn from that and get back to not conceding goals easily.''
The Phoenix have already signed former Melbourne Victory midfielder Carlos Hernandez, who will join the club after a stint in India.
Phoenix general manager David Dome said he was delighted Bertos is staying with the club.
"Leo is a core member of the squad,'' Dome said. "We began negotiations with him some time ago and I am really pleased he has agreed a new deal.''