Australian Nick O&aposHern has had to settle for a share of equal third at the St Jude Classic as Dustin Johnson held on to edge John Merrick by a stroke on the final day in Tennessee on Sunday. O&aposHern began the day equal leader with Merrick and Davis Love III but could only manage a one-under final round of 69, which included four birdies and three bogeys, to end up seven-under overall and two strokes adrift of Johnson. The Perth native, Northern Ireland&aposs Rory McIlroy and American Chad Campbell all had chances to tie at the last with a birdie, but all knocked their tee shots into the lake. Robert Allenby was the next best Australian on six-under in a tie for seventh. It was Johnson&aposs second tournament back after nearly three months out with a back injury and he announced his return superbly with a closing four-under 66 to finish at nine-under. Merrick, who remains winless on the Tour in 154 career starts, finished at eight-under and drew level at the 16th after back-to-back birdies before Johnson achieved the same feat on the 16th and 17th to regain the lead. Johnson came from two strokes behind to win his sixth career title, the only player on the Tour in their 20s to do so. Four players tied for third at seven-under in Campbell, O&aposHern, American Ryan Palmer and Love III. Ken Duke shot a scorching final-round 65 to move up to six-under with South Korean Seung-Yul Noh, McIlroy and Allenby. Australians Gavin Coles and Stuart Appleby finished at two- and three-over respectively while Steven Bowditch (seven-over) and Mathew Goggin (12-over) had tournaments they&aposd rather forget. On the Nationwide Tour, meanwhile, a six-over 78 cost Australian Scott Gardiner in the final round of the Mexican Open on Sunday as Lee Williams secured victory. Gardiner started the final round at the El Bosque Golf Club tied for second, but faltered to finish tied for 23rd at five under at the Nationwide Tour event. The New South Welshman holed two triple bogeys, three bogeys and three birdies in his final round. American overnight leader Williams held on to secure a one-shot win, ending up at 14 under and a shot clear of countryman Paul Haley II. Scott Gutschewski, also of the US, produced a six-under 66 in the final round for outright third at 12 under. In contrast to Gardiner, Australian Aron Price carded a seven-under 65 to finish tied for 25th at four under. Alistair Presnell (one under) and Steve Allan (even par) were also solid. Andre Stolz, the only other Australian to make the cut, finished at 15 over after shooting a horror 12-over 84 in the final round. His poor round included an eight on the par-three seventh and a 10 on the par-five eighth.