After 90 minutes without a goal, Watson's header broke the deadlock in injury time as the Latics capitalised on their man advantage following Pablo Zabaleta's late dismissal.
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"I've got to say, for 95 minutes today, we were outstanding. [It was] Fully deserved. I think we played Man City off the pitch," he told ESPN.
"And to come on and score the winner is a dream come true. I had a gamble at the near post and thankfully it came off."
Watson moved on to emphasise the importance of switching their focus to Premier League survival, while he was also eager to praise the people at the club that helped him after he broke his leg against Liverpool back in November.
"Yeah, it was a huge win. We know we've got two more games in the league and if we perform like that, we won't be far away. So we'll enjoy it for the rest of the day and then we'll crack on again tomorrow," he continued.
"It was a long six months. I worked hard, [and] was around some good people that got me through those six months. It's a dream come true."