Kelly only joined the club in January and a lack of match fitness and injuries meant he only had a watching brief until his moment in the sun on the final day.
But even from a distance Kelly knew what a task it was to get over the line.
“I couldn’t get over how difficult this league is,” he said. “One of the first games after I’d come here was Morecambe at home.
“They were near the bottom but they were a good side and could easily have won the game.
“I’m thinking, ‘This league is unbelievably difficult to get out of.’
“There are some huge clubs and no easy games.
“To get automatic promotion in a league like this on the resources the management have had is an unbelievable achievement.
“They have the ability to pinpoint and sign players. It’s incredible what they’ve done for this club.”
Despite months of inactivity, Kelly was the coolest customer when his moment of glory came as he produced a clinical first-time finish to send the Millers up.
While everyone else was stressed, the striker went into the zone.
“It’s funny,” he added. “In those moments everything slows down. Everything is just clear.
“You don’t think about where you’re at, you don’t think about what’s at stake, you don’t think about anything. You’re in the moment and instinct takes over.
“There’s a little flow and you’re in the zone. Nothing goes through your head. Chieo (Ogbene) made it easy because the weight of the pass meant I had to just hit it. I could have taken a touch but that would have made things more difficult. The roar. Wow. The place erupted.”