Darren Clarke today clung on to second place in the US Masters as Padraig Harrington failed to make the cut by the narrowest of margins when he finished on five over par.
Clarke completed a second-round 76 for a two-under-par halfway total at Augusta, four shots behind Canada's Mike Weir.
Weir added a 68 to his opening 70 to finish six under, with Clarke alone in second and another left-hander, Phil Mickelson, a shot further back.
Woods, seeking an unprecedented third straight Masters title, needed to par the ninth, his last hole, to qualify for the last two rounds.
The world number one pushed his drive right into the trees however, and could only punch out a low shot into a greenside bunker some 15 yards from the hole.
But not for the first time when under huge pressure, Woods delivered the goods with a superb bunker shot to three feet and holed the putt to card a 73 and five-over-par halfway total.
That was still 11 shots behind Weir, but having once come from eight behind Ernie Els in the final round to win an event, Woods could not yet be ruled out.
Els himself had fared much better in the second round, a best- of-the-day 66 repairing the majority of the damage inflicted by a first-round 79 and leaving the world number two seven behind Weir.
Woods had struggled to a 76 on Friday, his worst round in seven Masters as a professional.
It also brought his string of 257 consecutive rounds with at least one birdie to an end, a run stretching back to the third round of the 1999 Open, played in terrible conditions at Carnoustie.
It took until his 22nd hole of the tournament for his first birdie, but the 27-year-old missed good chances to increase his tally on the second and third holes when he resumed his second round this morning and remained two over par.
Woods already knew he would have to break yet another record to claim his ninth major title on Sunday, Craig Stadler's 75 in 1982 the previous highest first-round score by a winner.
And the size of his task increased significantly with a double bogey five on the fourth hole, Woods twice finding sand and dropping back to four over par, When he also bogeyed the par-three sixth hole he was five over for the tournament and now in serious danger of missing the halfway cut.
A birdie on the seventh appeared to give him some breathing space, but he then three-putted the par-five eighth for a bogey and the pressure was back on.