McIlroy won five times in 2012, including a second major title by eight shots, to finish top of the money lists on both side of the Atlantic but has yet to taste victory this season.
Down from first in the world rankings to sixth as a result, McIlroy is a lowly 62nd on the European Tour's Race to Dubai and needs to move into the top 60 this week to have a chance of qualifying for the DP World Tour Championship in November.
McIlroy is less than 4,000 euros (£3,400) behind Garth Mulroy in 60th place, but with next week's Turkish Airlines Open not currently on his schedule, he will need to win much more than that to feel safe.
The first prize of just over one million euros (£856,000) would of course take care of everything and McIlroy took confidence from his one-shot victory over Tiger Woods in their 18-hole exhibition match at Mission Hills on Monday, insisting he was more likely to win in Shanghai than miss out on a trip to Dubai.
And that did not appear to be an idle boast in the early stages of his first round, the 24-year-old starting from the 10th with a birdie and, after giving it straight back at the next, also picking up shots at the 12th, 14th and 16th.
That took McIlroy to three under par and just two off the lead held by Ernie Els, who was one ahead of Martin Kaymer, Jonas Blixt and Kiradech Aphibarnrat.
Luke Donald, playing alongside McIlroy and Dufner, was also three under after birdies at the 10th, 13th and 14th, while Dufner was two under.
The US PGA champion had holed his second shot to the 10th for an eagle - his ball spinning back some 25ft into the hole - and birdied the 15th before dropping a shot on the par-four 16th.
Els had also started on the 10th and covered the back nine at Sheshan International Golf Club in 33 with birdies at the 14th, 15th and 17th before picking up further shots on the second and third.
McIlroy left a long birdie putt inches short on the par-three 17th but made no such mistake from four feet on the par-five 18th to reach the turn in 32, before another birdie on the first took the former world number one into a share of the lead on five under.
Kaymer had also briefly shared the lead after his seventh birdie of the day on the seventh, only for the Ryder Cup hero to then spin his approach to the par-five eighth back into the water guarding the front of the green.
That led to a double-bogey seven and dropped the German back to three under.