The Estonian hitman found a combination of the Fir Park woodwork and shot stopper Radoslaw Cierzniak denying his bid to end a 19-game streak without a goal three weeks back, as Well lost a game they had dominated thanks to a late strike from Johnny Russell.
But Stuart McCall's men have responded strongly to that loss to string together an unbeaten three-game run with home draws against Dundee and Hearts coming either side of an emphatic 5-1 thrashing of Inverness in the Highlands.
Now the chance is there to avenge that defeat by Peter Houston's men and shoot Well to a vital three points that could lift them up into the top four of the SPL, helping them in their bid to return to European action next season. Ojamaa is bristling with intent.
The 21-year-old said: "The last game with United was a very frustrating one for me and for the team as a whole.
"To be fair their keeper Cierzniak had a great game, but I managed to beat him on a couple of occasions only for the woodwork to get in the way.
"We created so many good chances in that game so to not even get a point was very hard to take. But tonight we have the opportunity to try and get a result that would make up for that one and if we can create the same level of chances I am sure we will take them.
"But United are a good team and at their ground they will be a tough team to beat."
The Estonian is anticipating a vastly different game from Saturday's dull 0-0 draw with Hearts and believes that both sides' commitment to playing passing, fluid football will make for an entertaining game.
But as the Lanarkshire side head to a venue where they took four points from a possible six last season, the benefit of having recorded their first clean sheet since the opening day of the current campaign on Saturday was not lost on Ojamaa.
He said: "Fair play to Hearts, they are a very well organised side at the back and they are hard to break down.
"But we have taken plenty of positives from the draw even if it was not the most entertaining of games.
"To be keeping a clean sheet against them and backing up the win at Inverness with another solid result and performance is good.
"Now we need to carry that on and try and build on it at Tannadice. Given our last game with United, we're not short of motivation to achieve that."
With Well boss McCall set to field the same starting XI for the third fixture on the bounce, Ojamaa says confidence is high within the Fir Park ranks that success can once again be savoured on Tayside.
The Well front man said: "Even though we perhaps haven't been getting the results that we believe our play has deserved, we have been playing very consistently of late.
"If we can maintain that level we can definitely get something at Tannadice."