The Saints legend confirmed his retirement from playing on Wednesday, after 17 years at the top of the game.
McManus hailed the way that Wellens had helped to steer the club through some potentially rocky waters in recent years.
“Seventeen years is a staggering long time in rugby league,” he said.
“I think the least number of games he’s played in any one season has been 25, so he’s been an ever-present great during those 17 years.
“It’s a difficult day and a difficult time for us all, particularly Paul.
“He’s had a lot more highs than some players have had, and some great players as well.
“His achievements and trophies in particular have been quite remarkable.
“There couldn’t have been a more fitting occasion and a more fitting moment than the Grand Final.
“That was the end of Paul’s captaincy, and Paul captained the club in a difficult transition period for three or four seasons, when great players had retired from the club.
“We were going through a transition on the field. We had a season at Widnes, we were moving to a new home.
“It was a disruptive time for the club. His strength of personality and the respect that he had amongst his peer group in the team held everything together.
“It culminated in that wonderful triumph last October.”
The retirement adds more worry to Saints, though. Shannon McDonnell has been ruled out for the rest of the season in the last few days, leaving the club’s full-back resources bled dry.
“We’ve actually lost five full-backs with injury for the year,” he added.
“We’ve had one full-back for 15 years without interruption, and we’ve had to have five at the moment, and there could be others in the rest of the season.
“So it shows how resilient and robust he was as well as being a great player.”