England's David Lynn stormed to a one-shot lead at the halfway stage of the 1.8-million dollar Volvo China Open on Friday, playing through the pain after quick surgery in a back room of the clubhouse.
The 32-year-old, seeking his second European Tour title since turning professional a decade ago, went under the knife on Thursday after his opening four-under-par 68 at Beijing's Honghua International Golf Club.
He needed further surgery just before beginning his second round to remove a painful lesion in his groin that has been hindering his swing and affecting his putting stance all week.
Despite the inconvenience, he shot a five-under-par 67 with nine birdies to move to nine-under for the co-sanctioned Asian Tour and European Tour event.
Zimbabwean Marc Cayeux, Thailand's Prayad Marksaeng and Jose-Filipe Lima of Spain were a shot further back at eight-under par.
Defending champion Paul Casey followed up his opening 71 around the challenging par-72 7,203-yard Nick Faldo-designed course with a 68, moving to five-under for the tournament to remain in striking distance of the leaders.
Sweden's Henrik Stenson, the pre-tournament favourite, fought back after his disappointing first-round 73 with a 68, which included eight birdies, to lie six shots off the pace.
It could have been so much better but the long-hitting 30-year-old, ranked 13th in the world, found the water twice on the 429-yard sixth hole - his 15th - to record a quadruple bogey.
Taking advantage of the relatively benign conditions and starting from the 10th, Lynn, winner of the 2004 KLM Open, got off to a blazing start with three birdies in his first five holes.
He dropped a shot on the signature 422-yard 15th but picked up two birdies over the next two holes, only to give the shots back with a double bogey on the 18th after finding the water.
Coming home, the lanky Englishman recorded four birdies in succession beginning at the second but finished with a bogey on the 446-yard ninth after his ball plugged in a greenside bunker.