They loved the way their team began with a bang in this William Hill Scottish Cup fifth round tie when star striker Johnny Russell scored after just 16 seconds.
They loved the subtle changes that saw the zonal defending used by McNamara’s predecessor Peter Houston ditched and a greater freedom injected to the attacking play.
They loved the manner in which United dominated possession for long periods of the game, including keep-ball exercises of 20-plus passes.
And, let’s be honest, they loved rubbing it in to Rangers, beating the boycott by turning out in large numbers to snub a collective nose at all the pre-match controversy.
This was a commanding and comprehensive victory for the Tangerines.
It was all the more noteworthy for the fact that they had not won at Tannadice since August 19 when they saw off Dundee by the same 3-0 scoreline.
Thankfully, on Saturday the focus was on events on the pitch and not any animosity — real or imagined — between United and Rangers.
That was welcomed by man-of-the-match Willo Flood.
“It felt like everybody forgot there was a game of football happening,” said the Tangerines midfielder. “It was all about what this chairman was saying or that chairman or fans’ group was saying. I think showed that we were just concentrating on the game and we got a good result because of that.
“Hopefully, now everybody will be talking about Dundee United having a game plan, getting the ball down and passing it and deservedly winning the game.”
Let’s also hope that with this match out of the way a bridge of reconciliation can now be built between two clubs who, historically, have enjoyed an excellent relationship and shared some fabulous football matches over the years.
This was the third time in four seasons that United have knocked the Ibrox men out of the Scottish Cup. In 2010 they did so on the way to winning the trophy; last season’s victory came just before the demise of the oldco Rangers; and this one saw them outplay a side that is a shadow of its former self.
No visiting player had even touched the ball before goalkeeper Neil Alexander’s hand got to it but could not stop Johnny Russell’s shot hitting the back of the net after just 16 seconds.
Russell clipped the bar with a strike then, with Jon Daly given the freedom of the box by the woeful Rangers defence, the big captain rose unchallenged to head home for the second on 36 minutes.
The Ibrox men enjoyed a decent spell at the start of the second half but United were always in control and rounded things off on 79 minutes with a great third goal from Russell after he was played in by Daly.
With the game gone, Rangers lost their discipline and substitute Kal Naismith was given a straight red card for a challenge on Flood then Ian Black followed him into the dressing room after picking up a second yellow card for a tackle on John Rankin.
Black’s petulant slow walk off and his making as if to grab the corner flag did his side no favours. What a difference a season has made for the midfielder, who just last May was Hearts’ star man as they lifted the trophy by beating Hibs at Hampden but now was reduced to the role of petulant child.
The red cards made no difference to the outcome, though, with United on easy street by then.
For McNamara, it could hardly have been any better and the new boss sported a grin as long as Tannadice Street as he reflected upon his dugout debut.
“It was a great start for us and hopefully we will do that every week!” he said. “I thought we carried a real threat. We could have had a few more goals but I am delighted just to be through. We have some good players and you can see the threat we carry throughout the team.
“I am also delighted with the defensive side because we kept a clean sheet and it’s been eight games since we did that. As an ex-defender that really pleases me.”
For Ibrox boss Ally McCoist it was an afternoon to forget and he felt particularly let down by his senior players.
“It was certainly poor and probably our bigger players should have done better. It was a disappointing day for one or two who, with SPL experience, would hopefully have done better,” he said.
“When criticism is due and warranted, believe me, they get it. Some of the players got it after the game.”