Golf - PGA Tour:Graeme McDowell, Jose Maria Olazabal, Mathias Gronberg and mounted a strong European challenge at the St Jude Classic but it was American Brian Gay who led the way in Memphis.

Gay, who won the Verizon Heritage tournament in April by 10 strokes, shot an opening-round six-under-par 64 at TPC Southwind that featured just one bogey.

That had given him a two-shot lead over the rest of the field until compatriot Jimmy Walker carded a 65 with one of the final rounds of the day.

Spaniard Olazabal, playing on the PGA Tour for just the second time since April and without a win in the United States for seven injury-hit years, carded a bogey-free 66 to take a share of the early clubhouse lead in Tennessee alongside Sweden’s Gronberg.

They were joined late in the day by Northern Ireland’s McDowell as well as Americans Rich Beem and Chris Stroud in what became a five-way share of third place.

Olazabal, 43, tied for 36th at last week’s Memorial on his return to the US for the first time since missing the cut at The Masters in April and then tied for sixth at the Verizon Heritage.

“It was an excellent day,” Olazabal said. “I didn’t expect it, to be honest, but that’s the game of golf.

“I played pretty solid today and managed to score well. I have to say that the greens were a little bit softer after the rain, and I think that helped a little bit.”

McDowell started from the 10th tee with a bogey but moved to five-under with a birdie at his 15th hole.

The Portrush pro, though, bogeyed the seventh - his 16th - to fall back to four-under as he finished with a 66, while Gronberg had just one bogey, at the par-four 12th, in his four-under round.

Sweden’s Fredrik Jacobson added his name to the leaderboard with a 67, as did Welshman Richard Johnson.

World number two Phil Mickelson, returning to tournament play for the first time in a month since announcing his wife Amy was suffering from breast cancer, shot an impressive two-under 68.

Mickelson had underlined the need to return to competition to give himself a mental break as well as to prepare for next week’s US Open at Bethpage.

“It was a good way to get started,” Mickelson said. “It had a chance to be a low round because I made a couple early birdies but I finished with some birdies late to get it back to two-under.

“I’m pleased with the start. It’s certainly not going to be on top of the leaderboard but it didn’t hurt me any.”

Mickelson said his opening round had been everything he had hoped for in part due to his playing partners, fellow three-timer major winner Pádraig Harrington, who shot a two-over 72, and fellow American Cameron Beckman, who matched his compatriot with a 68.

“I thought the pairing I had, playing with Pádraig and Cameron was a perfect pairing to make the day light-hearted,” he added.

“We talked about a number of things that were not related to what’s been going on and so it’s been really good.”

Spain’s world number four Sergio Garcia and Scotland’s Martin Laird each shot a level-par 70 while Sweden’s Richard S Johnson and Jesper Parnevik shot 71 and 72 respectively.

However, two-time major winner John Daly struggled on his first day back on the PGA Tour having completed a six-month suspension for breaching Tour conduct policy.

The American, who had been playing on the European Tour during the ban, was in the tournament on a sponsor’s exemption but had to settle for an opening 72.

Players champion Henrik Stenson failed to continue his TPC Sawgrass heroics on his return to the USA, the Swede shooting a 73, as did compatriot Carl Petterson.