The former Arsenal youngster was an ever-present between the sticks before fracturing his ankle in a 1-0 defeat to Hartlepool United back in February.
He was restored to the side by manager Neal Ardley for Saturday’s goalless stalemate with U’s as Ross Worner dropped back down to the bench.
Shea only discovered he would be playing 24 hours earlier and admits even he has been shocked by the speed of his recovery.
He said: “I had done a bit of handling and came in on Tuesday after the Dagenham defeat. I had a bit of a workout and then rested on Wednesday to see how my ankle reacted.
“Thankfully it was fine so I trained on Thursday and Friday and played today. He named the team on Friday and I was a bit surprised to be honest. I’m glad to be back.
“We were never going to rush it. If there was a risk then they wouldn’t play me. If there was a chance that I could’ve damage my ankle more then I wouldn’t have played.
“There’s just no point in risking a worse injury.
“Macca and Ross have done really well since I’ve been out. We spoke all the time in training and I was here watching at every home game while I was out.
“We’re a tight-knit goalkeeping group and we all want each other to do well so I’m glad they did.”
Shea kept a clean sheet on his return to action against Oxford, although there were a couple of hairy moments and a collision with the post in the first half at Kingsmeadow.
He added: “The wind brought the ball in more and I just didn’t realise where I was in relation to the post.
“I felt good in the warm-up but when the game started and I was back in a match situation, I just felt a little bit rusty.
“It will take me a couple of games to get back up to speed. Hopefully with time and games I can get back to my best.”
Shea is expected to continue in goal for the trip to Plymouth on Tuesday night, while the Dons are hopeful the prognosis isn’t too bad on Deji Oshilaja after he was rushed to hospital yesterday.