The Bosnian midfielder was given his marching orders in the 20th minute as he pulled the shirt of Bradley Dack to prevent the midfielder from breaking clear into Boro’s box.
Initially, referee Simon Hopper appeared to have missed the incident, though he later received information via his earpiece to show Besic a straight red card.
Speaking about the incident, Pulis believes whether he accepted that Besic made a clear foul, he still thinks that goalkeeper Darren Randolph would have gathered the ball ahead of Dack.
Pulis said: “The referee doesn’t send him off – it’s the fourth official and the linesman on our side. I’ll say it now – Besic does pull his shirt.”
“But I believe our goalkeeper was getting to the ball first before their lad. I think it’s a yellow card, not a sending off.”
“How they make that decision from that distance – and a decision that ultimately changed the game – is beyond me. I think you’ve got to be 110 percent sure that you’re stopping him from scoring a goal or stopping a clear-cut chance.”
Adding salt to Boro’s wounds, Blackburn converted from the free-kick which followed the departure of Besic, leaving 10-man Boro chasing the game for the last 70 minutes.
To his credit, the changes made by Pulis at halftime galvanised the home side, with Britt Assombalonga coming off from the bench to score an equaliser to level the game.
Pulis added: “The second half was good. I just thought the sending off completely knocked the stuffing out of the lads.”
“It was disappointing for Ashley Fletcher because we wanted to play him a little bit on the left-hand side, cutting in, and I think that was working quite well up until the sending off.”
“Bringing Lewis Wing on, I decided to play him and Jonny Howson to try to get around Jordan Hugill as much as they possibly could.”
“When we got the ball, at least we were playing with three players up there, not Fletch just coming off that one side. Then in the second half, you bring Britt on and you take a chance.”
Saturday’s result means that Boro are out of the Championship’s top four, with 7 points separating them from 1st placed Norwich City.