The Wigan midfielder almost joined Boro before rejecting a move to The Riverside and instead opting to move to The JJB Stadium after leaving Crystal Palace.
Watson will now get an early chance to come up against Boro as Wigan travel to Teesside on Saturday.
The 23-year-old insists he has no regrets about choosing Wigan over Boro.
"It was a tough decision but I think I made the right one. I was at Palace for
13 years and I think it was time for a change," he said.
"I was up in Middlesbrough and my agent made me aware Wigan were interested and as soon as I knew that I wanted to speak to them.
"I spoke to Steve, who was gaffer at Palace when I was a young lad there, and he was straightforward with me.
"He spoke highly of the club but walking into the training ground there was a buzz about the place.
"Being seventh in the Premier League you are going to be on a high and the lads were buzzing and that was probably the main factor.
"Wigan are in a fantastic position to crack on and push up the table even more."