Five-time major winner Phil Mickelson showed few ill effects after being forced to change his caddie on day two of the £7.9million WGC-Mexico Championship.

Mickelson's long-time caddie, Jim 'Bones' Mackay, lasted just three holes of Friday's second round before being forced to leave the course due to a stomach virus which has affected several players in Mexico City.

Fortunately for Mickelson, his brother Tim had been alerted to the problem and was on hand to take over on the bag as his sibling looked to remain in contention for a third World Golf Championship title.

Starting on the back nine at Chapultepec Golf Club, Mickelson carded two birdies and one bogey in his first 11 holes to reach five under par, two shots behind England's Ross Fisher.

Fisher had also started his round from the 10th and picked up shots on the 11th, 15th and 16th to spearhead a strong European challenge, with Rory McIlroy just a shot behind on his return to competitive action.

McIlroy had played just once previously in 2017 due to a rib injury which saw him push through the pain barrier before losing to Graeme Storm in a play-off for the South African Open in January.

The 27-year-old still arrived in Mexico knowing that he could reclaim top spot in the world rankings for the first time since August 2015 by winning his third WGC title, as long as current number one Dustin Johnson finishes joint fourth or worse.

McIlroy started his second round by driving the green on the short par-four first before three-putting for par, but then birdied the second, fourth and sixth to reach six under.

On a highly-congested leaderboard, England's Andy Sullivan and Tyrrell Hatton were alongside Mickelson, Jimmy Walker and Roberto Castro on five under, with Lee Westwood and Johnson a shot further back.