Hunter Mahan gave up the chance of a million-dollar pay day as he pulled out of the RBC Canadian Open when his wife went into labour.

Armed with a two-shot lead heading into the third round, Mahan was all set to head to the first tee when a particularly important call came in.

Mahan was going through drills at the driving range when he heard the news from wife Kandi.

There was no doubting what Mahan would do, as he immediately headed back to his Dallas home.

With conditions favourable for low scoring at the Glen Abbey course in Ontario, the likelihood is that Mahan would have built on his lead and advanced his chances of a first title of the season. The top prize this week is just over one million dollars.

Mahan said in a statement on "I received exciting news a short time ago that my wife Kandi has gone into labour with our first child.

"As a result, I have withdrawn from the RBC Canadian Open to return to Dallas. I would like to extend my very sincere gratitude and appreciation to RBC and the RBC Canadian Open.

"Kandi and I are thrilled about this addition to the Mahan family and we look forward to returning to the RBC Canadian Open in the coming years."

Brandt Snedeker took advantage of Mahan's withdrawal by shooting to the top of the leaderboard, as a 63 took him to 14-under 202, placing him one ahead of Sweden's David Lingmerth and two clear of fellow Americans Matt Kuchar and Jason Bohn.

Lingmerth signed for a 65, Kuchar a 64 and Bohn a 66.

Dustin Johnson had an eagle three at the 18th in a 63 that took him to 11-under 205, alongside fellow US players Kyle Stanley and Charley Hoffman, and England's Greg Owen, whose 67 was his lowest score of the week so far.

Snedeker was realistic in admitting Mahan would probably have stayed out in front, had he not had to attend more important business.

Mahan, 31, has won over two million dollars on tour already this year, and 24 million dollars over his career, so his choice today was never that of choosing one life-changing prospect over another.

"With him leaving, it left the leaderboard wide open," Snedeker said. "It changes the complexity of the tournament. The way Hunter was playing, he was going to be hard to catch ... anyone can win now."

While Owen was putting himself into contention, Northern Ireland's Graeme McDowell's topsy-turvy form continued.

Having started with a 76 and followed that with a scorching 65 yesterday, McDowell added another 76 to be squeezed out of the tournament along with three others under the PGA Tour's MDF (made cut, did not finish) rule.

That is enforced effectively as a Saturday cull after over 70 players make the halfway cut, to keep the field at a more manageable size for the final round.

"Another strange day at the office," McDowell wrote on Twitter. "Didn't drive it great and putted awful.

Been working so hard on my long game lately putting has suffered."

McDowell, who missed out by two shots, still thought he was in the tournament long after coming off the course.