Jordan Spieth hangs on as winds create Masters havoc, Rory McIlroy moves into contention

When the dust had settled on a windy day that kept the Georgia pines bending and pin flags waving, defending champion Spieth was still holding top spot -- but just barely, watching a five-shot lead chopped to a single stroke after an adventurous two-over 74.

McIlroy, who began the day four shots adrift of the pacesetting Texan and fell a massive eight back with seven to play, stormed into contention a blistering back nine charge and the help of a Spieth stumble.

The Northern Irishman appeared headed in the wrong direction as he covered the outward nine in one-over but caught fire after the turn, plundering three birdies over his final six holes for a one-under 71, equal to the lowest round of the day.

New Zealand's Danny Lee (74) and American Scott Piercy (72) sit two off the lead with Japan's Hideki Matsuyama (72), Denmark's Soren Kjeldsen (74) and American Brandt Snedeker (72) one further back after a wild and woolly day that saw just seven men under par as the year's first major hit the midway mark.

Spieth had slept on a two-shot overnight cushion and by the time he stepped onto the first tee to start his second round his advantage had grown to three with none of the early starters able to mount a serious challenge on another sunny, gusty day.

The world number two went quickly to work, drawing a huge roar from the large gallery tracking him when he rolled in a 14-foot birdie putt at the first that put even more pressure on the chasing pack.

Spieth continued to pull away with an easy birdie at the third after a pinpoint approach left him a two-footer to get to eight-under.

But danger lurks everywhere at Augusta National, and Spieth found it at the par-four fifth where he four-putted and ran up a double bogey that slashed his advantage to three.

Spieth hit back with a birdie at the eighth but stumbled through the turn with bogeys at nine and 10 followed by back-to-back bogeys at 16 and 17 before a draining a nervy 14-footer for par at the 18th to keep the outright lead.