The 33-year-old achieved the rare footballing feat last Saturday when he helped Reading clinch the Championship title on the same, bittersweet day that cash-strapped Pompey were relegated into League One.
Now the Reading-born midfielder is desperate to join his hometown club on a permanent basis and will sit down with manager Brian McDermott in the next few weeks.
"Getting promotion with Reading has been fantastic," declared Mullins. "To come back to Reading and for the club to be promoted to the Premier League is amazing.
"But it's been a bit of a weird season for me having left Portsmouth only to see them go down. I still know all the staff there and I'm still contracted to Portsmouth.
"All in all, it's been a bit of a difficult one for me really. It's definitely easier to be at the top of the table than it is at the bottom.
"Nobody wants to be relegated but unfortunately Portsmouth have and it's going to be hard for them to get back up next season."
Mullins is a big hit at Fratton Park having won Portsmouth's Player of the Year last season.
But the south coast club is riddled with debt and Reading could offer Mullins a timely escape route.
"The move to Reading was a loan move with a view to a permanent deal," he explained. "We will sit down in the summer and see if we can sort something out.
"Obviously I'd love to stay at Reading. It's my hometown club, we've just been promoted and there's a great feeling around the place.
"I'd love to be part of it next season but at the moment that's a long way off."
Mullins slipped through Royals net and was snapped up by Crystal Palace as a teenager before moving to West Ham United where he spent several years in the Premier League.
He joined Royals on loan in mid-March and proved a versatile signing after appearing at right-back and in central midfield.
Mullins also helped soften the blow when midfield dynamo Jem Karacan broke his ankle in a fiery victory over Leeds United earlier this month.
Now, whatever the future hold for Mullins, he is determined to finish the season on a high by winning at Birmingham City this Saturday.
"We'll be going all out to win," he stressed. "The manager said that's what he wants us to try and do."