World Snooker 2011: Williams defeats Day to progress
Mark Williams came out on top of the all-Welsh match in Sheffield by beating Ryan Day 10-5 to reach the second round of the World Championship.
The two-time world champion resumed at 6-3 after bagging a 137 break in the first session and took advantage of a cruel kick for Day to go four ahead.
Day clawed back two frames, only for the world number two to produce runs of 89, 70 and 66 to secure victory.
The 2008 finalist Ali Carter survived a scare but overcame Dave Harold 10-3.
Carter had cruised into an 8-1 lead but had to watch Harold pinch the evening's opening two frames before securing victory with a 61.
Essex's Carter, whose highest break of the match was only 80, will next play either Graeme Dott or Mark King and said: "It was a tough game. It was always going to be."
Harold at least had something to celebrate after watching his team Stoke City reach the FA Cup final. A card signed by the team had sat on his table throughout the encounter.
Meanwhile, Williams looked in ominous form yet again coming soon after his German Master triumph and should be regarded as one of the favourites this year as he eyes a third world title following his 2000 and 2003 glory.
Although delighted to make round two after coming through quite comfortably in the end, Williams was upset for his practice partner who is struggling to stop a slide in the rankings.
"I'm over the moon," the 35-year-old left-hander Williams said. "It was a funny victory though because I didn't enjoy winning that one. It's hard playing someone you practice with. I'm very disappointed for him."
After powering into a 6-3 lead on Saturday thanks to a 137 break - the highest of the tournament so far - and runs of 71 and 84, Williams always looked in control, despite his opponent opening up a 52-0 lead in the evening's first frame.
A shocking kick on the red left Day fuming in his chair and Williams calmly strode to the table and cleared up with a 55 to deliver a sucker punch to his close friend.
The pair were often seen exchanging jokes between the chairs, but between the banter, it was clear Day was still full of fight and he roared back with a 66 and 43 to reduce the deficit to two.
That recovery soon came to a halt as the mistakes increased and Williams surged into the second round with breaks of 89, 70 and 66 to ease to his uncomfortable victory.
Day, who has dropped out of the top 10 and is currently 24th, said: "It's disappointing. Most of the damage was done in the first session and I didn't give myself much of a chance.
"My mindset was wrong. I showed Mark too much respect going into the game."