Mark Williams admitted he had dragged opponent Matthew Stevens down to his level to claim a 6-4 victory and reach the quarter-finals of the Betfair Masters.

Williams was completely out of sorts as he trailed 4-1 and saw Stevens on the verge of winning the sixth frame as well.

But Stevens missed a simple brown to go 5-1 in front and from then on committed numerous basic errors as Williams took five frames in a row to secure an unlikely victory.

"I didn't play very well at all to be honest, neither did Matthew," Williams told BBC2.

"He missed a sitter of a brown for 5-1 and I don't think I'd have come back from 5-1 to be honest.

"Even though I wasn't playing too well I was still trying 100 per cent, and perhaps that's got what me through in the end.

"It's easy to win when you are playing well, but it's hard when you're not playing too well and I was getting hammered out there really. I'm over the moon that I just stuck in there, tried my best and managed to turn it around somehow.

"Matthew helped me out a lot, he missed a lot of balls he normally wouldn't miss. Perhaps I dragged him down a bit and pounced on him.

"Coming into this tournament I practised really hard and was probably playing the best I have for years and years, knocking 147s in every single day near enough.

"I was quite confident coming up here and then I go out there I can't make 47. If I can bring the practice to the match table I've got a chance, but I just can't do it at the minute. I might be trying too hard."

Former world championship finalist Stevens looked in complete command of a low-quality match when he led 4-1 and made a break of 59 in the sixth frame.

Williams made 37 to get back into the frame before missing a straight yellow, but Stevens then missed an equally easy frame-ball brown to let his fellow Welshman off the hook.

The left-hander improved from then on and runs of 59 and 68 helped him into a 5-4 lead, while he sealed victory with breaks of 48 and 44 after Stevens had missed a black off the spot.