* Defending champion Willett, Stenson at risk of missing cut
* McIlroy five shots off the pace after a 73
* Masters rookie Rahm three back of clubhouse leaders (Adds later details)
AUGUSTA, Georgia, April 7 (Reuters) - Sergio Garcia charged into a share of the clubhouse lead with overnight leader Charley Hoffman in the second round of the U.S. Masters on Friday to boost his hopes of a maiden major title.
Players were greeted by sunny skies, but chilly and windy conditions made for challenging scoring at the year's first major where defending champion Danny Willett and world number five Henrik Stenson were likely to miss the cut.
Garcia, who has never finished higher than eighth here and started the day six shots back, mixed six birdies with three bogeys in tough scoring conditions at Augusta National for a three-under-par 69 that left him four under for the tournament.
The 37-year-old Spaniard overcame a brief scoring scare as the tournament's scoring system had showed he made a triple-bogey at the par-four 10th.
Garcia hit a provisional ball following a poor tee shot but found his original ball, which had ricocheted off a tree and into the fairway, and went on to make a bogey five instead of incurring a two-stroke penalty.
Three-times champion Phil Mickelson, Australian Jason Day, American Jordan Spieth and Olympic champion Justin Rose were among the late starters.
Hoffman, who made nine birdies in a brilliant opening round to lead a major for the first time, was in control as he birdied the second but he fell apart with five bogeys in a six-hole stretch mid-round.
William McGirt started the day four shots behind Hoffman and offset two bogeys with a pair of birdies before dropping another shot at the 18th to slip to two under.
Defending champion Willett (78) got his round off to a miserable start by making a quadruple-bogey eight, while Swede Stenson (75) was also in danger of missing the projected cut of six over.
World number two Rory McIlroy (73), the highest-ranked player in the field after Dustin Johnson withdrew on Thursday, struggled to make a move as he mixed five bogeys with four birdies to sit five shots off the pace.
The Northern Irishman needs a win this week to complete the collection of golf's four major titles. (Editing by Ed Osmond and Andrew Both)