Stubbins has been in the firing line of fans and Professional Footballers Australia over his role in the purging of the player group and a season which brought the wooden spoon with just three wins in 27 matches.
But with the Jets showing signs of improvement in the final six rounds of the season as they picked up victories over Western Sydney Wanderers and championship winner Melbourne Victory, Mullen puts a more positive perspective on his experience under Stubbins, whose position is under review as he heads back from a scouting mission in Europe.
"I arrived in February (from Western Sydney Wanderers) and was received really well by the fans, the players and Stubbsy included," he said.
"My time there was enjoyable and that’s the reason why I decided to extend my contract for another two years.
"For me personally, I thought training was good and the team played some good football and there were certainly some improvements at the back end of the season.
"I came with an open mind and while it was tough results wise, I feel the performances were encouraging. Hopefully that’s a sign of things to come next season."
Mullen, 25, spent four years under Stubbins’ tutelage at Adelaide United, where the Englishman was assistant coach under Aurelio Vidmar in the team which famously reached the 2008 AFC Champions league final.
His arrival at the Jets came just a week after the club sought to cancel the contracts Joel Griffiths, Billy Celeski, Adrian Madaschi and skipper Kew Jaliens and David Carney.
When that failed they were forced to train alone and were exiled from the first team for the remainder of the season.
"For me, it was about getting some game time and it was enjoyable for me to come to Newcastle," Mullen added.
"I came at time when that stuff had already happened and I was fortunate that I didn’t have to see any of that."
While reluctant to buy into the charged debate over Stubbins's future, Mullen would be more than happy for the coach to be given the chance to fashion a squad in his own image while FFA seeks long-term ownership for the club after seizing the licence back from Tinkler.
"I had a good relationship with Stubbsy back in Adelaide and that was part of the reason I decided to come to Newcastle," Mullen said.
Stubbins wants the opportunity to turn the Jets' fortunes around by building from ground zero in the vein of Ange Postecoglou at Brisbane Roar where he culled a catalogue of big names when he took charge in 2009 before going on to win the A-League title the following season.
The departures of skipper Taylor Regan, James Virgili, Sam Gallagher, John Solari, Allan Welsh and Travis Cooper after the final round further antagonised some bewildered Jets fans with just 15 players remaining on the roster.
But Stubbins showed an eye for talent with his two February signings– Korean left back Lee Ki-Je and Serbian midfielder Enver Alivodic - making a real impact.
"Enver is a quality professional who worked as hard as anybody I’ve ever seen and a great player to have in your squad," Mullen said.
"Ki-Je is something special and is one of the better players I’ve ever played with.
"Technically he’s unbelievable … some of the stuff he does at training which you don't get to see in the games is quite phenomenal. They are two great signings who have really helped the team.
"And (defender) Nigel Boogaard (from Adelaide) is also going to be a great signing for us and will bring buckle loads of experience next season when he returns to his home town."
Mullen believes the people that truly matter are those long suffering supporters who have not seen the Jets qualify for an A-League finals campaign since winning the championship in 2008.
"They are the ones that pay the money to watch us play and support us and without them there is no Jets," he added.
"You want to do well and win for them and that’s the biggest disappointment looking back at last season.
"We want to repay them and you could see at times how unhappy they felt. Hopefully next season we can give them something to smile about.
"I am looking at everything that has happened as a positive and a fresh start. It's most important that we get the fans on board - it's really all about them."
