A first-half opener from Pavol Safranko and a controversial second after the break from Paul McMullan killed off potential play-off opponents Caley Thistle in the Highlands, though United would need a minor miracle in the shape of a goals avalanche to topple champions-elect Ross County.
The Tannadice team made County wait for a title party, with a point still required to complete the job arithmetically, but manager Neilson only had eyes for the play-offs.
Neilson said: “It was all about our attitude coming into it. It secures us second place today. It is important we keep building that momentum going into the play-offs, giving game-time for some of the players and rest for others. It is just trying to manage everything until we get to those play-offs, because it is so important to us.”
Even in defeat, Caley Thistle clinched a play-off place against Ayr United, but the hosts were unsurprisingly furious at the circumstances surrounding a clear handball by McMullan ahead of the crucial second goal and Brad Mckay’s late red card.
Tom Walsh saw a tremendous 35-yard hit tipped over the bar by keeper Benjamin Siegrist after 23 minutes but, four minutes later, the Taysiders were in front.
From Peter Pawlett’s flick-on, Safranko controlled and swerved a lovely left-foot volley from 15 yards inside the left hand post.
The Highlanders worked hard to hit back and a reverse head-flick from Jamie McCart flashed just wide of the left-hand post.
Just five minutes into the second period, though, United went two up. The Caley Thistle defence halted when the ball seemed to hit McMullan’s arm in the build-up, but he played to the whistle and waltzed on through the bodies in his path to net from inside the six-yard box.
Mckay then took two yellow cards after going down in the penalty area under Jamie Robson’s attentions. Booked initially for diving, referee Greg Aitken seemed to take exception to the defender’s reaction and flashed a red card.
Home manager John Robertson said: “We would rather have done it off our own steam, but we have achieved the play-offs – and that was our primary aim.
“There wasn’t much between the teams. It was one wonderful strike, a top drawer goal from Safranko, and then the other one was a handball.
“The player has admitted it was a handball but the man that counts missed it. It’s a really poor decision from the referee, as was the sending off. That did not detract from the best team winning.”