O'Sullivan was just 17 years old in 1993 when he beat Stephen Hendry in the final of the UK Championship at the Guild Hall in Preston, and now at the age of 38 he is very much the man to beat, having won four titles already this season.
He looked in control throughout against Donaldson and made top breaks of 109 and 73 to set up a last 16 match with Yu Delu, a 4-2 winner in a Chinese derby against Liang Wenbo.
"I got off to a good start and I think that maybe put a little pressure on Scott," said the Rocket, who won his 26th ranking title at the Welsh Open earlier this month. "I feel a little bit rusty, but each match I played in the Masters and the Welsh I got more into it, so I'd rather be underplayed than overplayed. I still feel like I'm a little way off sharpness but as long as I can win my first match and my second match then it should click in, I'll gather momentum and get sharper as the tournament goes on."
Ryan Day edged out Stuart Bingham 4-3 in a match characterised by mistakes by both players. Welshman Day looked certain to win 4-2 until he missed a pink to a centre pocket at 49-0. Bingham made a 59 clearance - the highest break of the match - but couldn't take an early chance in the decider and Day took it with an impressive run of 50.
"It was quite a poor game, I had no fluency at all," admitted Day. "I just took my eye off the pink in the sixth frame. I did that a couple of times in the match, which is something I'll have to cut out. I was pleased to make the break and pot the kind of balls that I did in the last frame.
"I thought I was playing too slow and bogging myself down a bit so it's something I'm going to try to change - just to try to get on with it and let it flow a bit.
"There's a big prize to play for here so everyone's going for that. It's a great set up here at the Guild Hall and there was a good buzz out there today."
Mark Allen was in fine form in a 4-2 win over Jamie Jones, compiling breaks of 136, 94 and 107.
"I played well the whole game," said the Antrium cueman, who was watched by former Northern Ireland footballer David Healy. "I was a little bit bemused how I was 2-1 down but I finished the match off really well.
"I seem to play better at this time of the season but I don't know why, I don't do anything different. It's purely coincidental. I practise as hard for the tournaments at the start of the season, for some reason or other it doesn't seem to happen. If you can get to the later stages of some events, no matter what period of the season it is, then you've done alright."
Ball by ball scoring and results from tournaments