Celtic dominated the match for long periods and finally earned their place in the Betfred Cup final thanks to a 87th minute strike from Moussa Dembele.
The pre-match favourites were unhappy they didn’t take the lead sooner when Erik Sviatchenko sent a header past Rangers goalkeeper Matt Gilks, only to see the effort disallowed for a foul on Clint Hill.
Replays appeared to show the challenge was six of one, half a dozen of the other, with the BT Sport commentary team in agreement that the goal was wrongly ruled out. Earlier in the match, Rangers thought they’d been awarded a penalty, only for the referee to book Barrie McKay for diving.
While he believed Thomson got it wrong, Webb - who once took charge of a World Cup final and now works for BT Sport as a referee correspondent - defended Thomson’s decision to blow for a foul while Sviatchenko headed home.
He said: “I love listening to these commentators and people who cast judgement. Craig’s got one view.
“It’s all about angles. It’s a crowded penalty area. There’s a bit of contact. Clint Hill probably, what we would call, ‘old mans’ Craig Thomson by going down easily, throwing himself a little bit. But, you know, at full speed I can totally see why Craig has disallowed it.
“Do I think he should have given a goal? Yes I do, but I’ve got the benefit of sitting here watching replays.”
As for the referee’s overall performance, Webb praised Thomson for how he handled the red-hot intensity of an Old Firm derby at Hampden.
He said: “Overall, Craig did ok. He kept his cards in his pocket - we had four in the end but three came late on.
“He got the penalty shout early on right. That was the important thing, to get that right. I thought the yellow card for simulation was a little bit on the harsh side, but he got the penalty call right.
“Overall, nobody is really talking about him. He got a bit lucky that Celtic scored so late.”