McClaren said: "We hope it's [the win] a catalyst but there's still a long way to go before we can say that.
"But it was an important win, we've had a tough week and we needed some pride back.
"Today was to say we don't concede any [goals] and can keep a clean sheet because we've got players who can score goals and be a threat.
"It was a performance I wanted to see from them - battling, full of character, full of attitude, getting blocks.
"We call it a horrible win, an ugly win and I don't think I'll be watching it on the coach on the way home."
"We said at half-time it's one of those games where they'll be one moment, at the most two, and make sure you take the moment," added McClaren.
"I think that's what Ishmael Miller has to do, he has to score more ugly goals like that, rather than spectacular ones.
"He's a threat - big and strong and direct - and with [Robbie] Findley they caused problems, so I'm delighted he's come in and got the goal."
Watford boss Sean Dyche rued that one defensive lapse, saying: "That was a negative that cost us in a cruel game where we're certainly good value for a draw."
The Hornets certainly had the chances to take at least a point.
"There's four [chances]," continued Dyche. "It's one of them where that's the difference in a game sometimes - a soft mistake and four chances where you're looking to score a minimum of one out of four.
"We played well, we controlled large parts of it [the game], we were well aware of their change in tactical shape before the game so we knew that and for a large part we delivered very good parts of our performance. It can be cruel sometimes and it was cruel tonight I felt."
The Watford boss added: "If we keep performing like that we're going to win football matches, that's the big deciding thing, performance levels, and I'm a great believer in them."