Keillor-Dunn smashed unerringly into the top corner in the 90th minute following a smart knock-down from Aden Flint to rescue a point.
“If you can't win then don't lose,” he said. “You have got to try and get something from the game if you can't win. It wasn't quite coming off today, I don't know why.
“They defended well and made it hard for us, luckily we got the goal in the end.
“We kept knocking on the door and staying in the game and we got our point.
“We want to try and stay unbeaten and keep climbing the league.
“We know we could have played better so it's a bit disappointing. We wanted all three points but that’s how football goes sometimes.”
And Keillor-Dunn, who has now banged in seven League Two goals, is hoping his fine scoring form can continue.
“It dropped on my toes and luckily it went in,” he said. “It was nice in front of the away fans.
“I knew I had to get in and around the ball. Flinty (Aden) has a good presence and can cause a threat anywhere on the pitch.
“I just have to keep getting in the box and being effective, to get on the end of things and to score as many as I can.”
Inside the opening minute the U’s went close when Jayden Fevrier let fly, only to see his effort blocked.
The Stags replied with Louis Reed firing narrowly over the top following some neat approach play by Hiram Boateng.
As the lively start continued, Stags’ Lucas Akins tried a curling strike which drifted just the wrong side of the post.
As the Stags continued to press for an opener, defender Aden Flint eased forward before drilling a shot from distance narrowly over the top.
Just when a Stags opener was looking the most likely, the U’s opened the scoring after half-an-hour.
Joe Taylor slotted neatly past Christy Pym following Arthur Read’s tee-up.
Samson Tovide came close to doubling the hosts’ leading before the break.
Keillor-Dunn came close with the Stags’ first opportunity of the second period, though he ought to have done better when shooting straight at the keeper.
Keillor-Dunn then found himself presented with another great chance from Jordan Bowery’s cross, but he headed over the top from just eight yards.
However, Keillor-Dunn came to the rescue in dramatic style.