Sullay Kaikai’s first-half brace set the U’s on their way to a first home win in three months and Tom Elliott sealed the three points late on after Rakish Bingham’s goal reduced the Stags’ deficit.
After the game, Murray hinted at big changes to the squad over the summer.
He said: “It just proved all the thoughts I had about certain things right, I didn’t learn anything today.
“I could have been ruthless with a few of them but it’s not worth the energy, I’ve wasted enough energy on certain individuals.
“I said before the game in the team meeting that you could get your trousers pulled down today because I know the group inside out.
“I’ve known what’s missing for a few months. I warned them what could happen if they weren’t on their mettle. I told them the first 20 minutes would be huge, make good decisions, play your way into the game, they’re going to start bright.
“Story of the season: the group’s not good enough in a lot of areas.
“It will be changed. This is a club that I love dearly and I make a promise now with the whole of my heart to the fans that I’ll never put a team out that doesn’t have 100% commitment and care towards the job in hand.
“If I was some individuals I’d hurt, not as footballers but as people.”
Cambridge boss Richard Money was relieved to see his side finally secure their League Two safety.
The result was only their third win in 20 league outings and their first at home since January 17.
“It was important that we got the number of points required through what we did, not what other people couldn’t do,” said Money.
“I thought the focus in the group in the first half was very good, we played with a good tempo but we gave a poor goal away and suddenly it becomes nervous.
“Unless you’ve played under those types of nerves it’s difficult to explain to people what it actually does. But we got the third one and it obviously eased the tension a little bit and it was important that we did it ourselves today. I’m really pleased that we have.
“We went for an attacking line-up and I thought we were very good, very strong defensively and very dangerous and creative in the important areas of the pitch.
“The first half was pleasing, the second half was a little bit like what we’ve watched here for a number of weeks.
“There’s a lot that I need to ponder on over the next couple of weeks. I don’t want to say too much right now but there’s quite a bit that I want to say.”