SAN FRANCISCO -- Opportunities abound Sunday as the fourth round is underway at the 112th US Open, the Olympic Club's Lake Course figuring once again to be a stern test to identify, as the US Golf Association likes to say, the best players in the world.

But will the fourth round be the final round? With Jim Furyk and Graeme McDowell tied at 1 under par, and 15 others within five shots of the lead, the possibility of an 18-hole playoff on Monday certainly exists, something that hasn't happened since 2008, when Tiger Woods beat Rocco Mediate.

With the leaders not teeing off for another four-plus hours, let's address some of the main topics for today, and answer a few questions.

1. Does anybody within five shots have a chance? When the foursome of players at 4 over includes Woods, Retief Goosen, Martin Kaymer, and Matt Kuchar, I'd say yes. They'll definitely need an under-par round, and probably some help from Furyk and McDowell, but those four players five back have to think they can win if they put a great, early number up, maybe a 65. The best round of the week has been 66, by Michael Thompson in the first round, so it won't be easy.

2. Can Beau Hossler keep hanging around? Maybe the best story so far has been the play of the 17-year-old amateur, who sounded convincing when asked if he can win this US Open. "Absolutely," Hossler said after his third-round 70. "There's not a doubt in my mind." There's doubt in mine. He's 3 over, four back, and probably needs something really low to give himself a chance. Reminds me a little of the 1998 British Open, when a 17-year-old Justin Rose charmed the golf world and tied for fourth.

3. What will Tiger Woods do today? You'd have a better chance of writing multiple scenarios down and picking them blindly out of a hat than accurately predicting what Woods might shoot. Nobody knows what Woods will do, that's his new normal (as Jamie Lee Curtis would say). Just when it seems he's in control, he shoots 75. The guess here is that he'll shoot 72 and be a non-factor today.

4. Can Furyk or McDowell overcome Olympic's history? The US Open has been played here four times before, and every time the 54-hole leader did not win. Sleeping on an Open lead can't be easy; it might be slightly easier for Furyk and McDowell because they're tied, so the pressure isn't falling completely on their shoulders. They know they have work to do if they want to win this tournament for a second time.

5. Who wins? I predicted Lee Westwood in print on Thursday, so my heart says keep backing the Brit as he tries to win his first major. What a story that would be. My head, though, says McDowell. He has the right approach to US Opens, his game has been sharp, and he thrives under pressure (this is a Ryder Cup year; remember, McDowell clinched the cup for Europe two years ago by winning the final singles match). I'll say McDowell beats Furyk, Westwood, and Ernie Els by one, the same victory margin as at Pebble Beach two years ago.