Jason Day has won his first match at the WGC – Dell Match Play but he may have paid the ultimate price.

Jason DayTaking on Graeme McDowell, Day was two down through four holes but fought back to be leading after 9 holes.

The highlight of Day's round came at the 370 yard par-4 5th hole when he drove the green but the low light of his round came at the 15th hole when he strained his lower back during his tee shot.

Clearly in pain, Day was able to half the next two holes and defeat Graeme McDowell 3&2, effectively ending the match after 16 holes.

Heading straight from the course into treatment a cloud now hangs over Day heading into The Masters which tees off on the 7th April.

With Augusta looming it's unclear if Day will continue at the WGC – Dell Match Play with his next match scheduled against Jaidee Thongchai on Thursday afternoon US time.

Of the other Aussies in the tournament Marc Leishman halved his match against Ryan Moore despite leading the match until the very final hole.

Adam Scott also halved his opening match against Belgian Thomas Pieters who fought back from being two down with three holes to play.

Marcus Fraser suffered a 4&3 at the hands of Zach Johnson. The Open champion was in control of the match from the very first hole.

Matt Jones had a tough battle against ISPS HANDA Perth International champion Louis Oosthuizen but eventually went down to the South African 2&1.