SAN FRANCISCO - They are the two most compelling holes this week at the Olympic Club. One bends left for practically 5 miles, the longest hole in U.S. Open history. The other beckons players to reach the green in two shots, then smacks them for daring to try.

No. 16 and No. 17 are the only par-5s on the Lake Course for this Open -- and they will play a pivotal role in deciding which player hoists the sparkling silver trophy.

No. 16 measures 670 yards on the scorecard, though U.S. Golf Association officials probably will use the new way-way-way-back tee for only two of the four rounds. No. 17, a par-4 in previous Opens at Olympic, tips the scales at 522 yards, but players must navigate a fairway and green both tilting sharply to the right.

It's unusual to have par-5s on consecutive holes, especially this close to the finish (Baltusrol Golf Club in New Jersey might be the only comparable layout in a major). The striking contrast makes it work, and will make players think as they steam down the stretch Sunday.

"Those two holes are so completely different," USGA executive director Mike Davis said. "On one, you've got this giant dogleg that seems to go on forever. The other one you're standing on the tee thinking, 'How do I hit that fairway?' Then if you hit the fairway, 'How do I hit the green?' Then if you miss the green, 'How do I get it on the green?'"

It requires little imagination to picture some loose-lipped pros bemoaning the tinkering to these two holes. Davis added the tee at No. 16 to make it a true three-shot hole, as it was in the old days, but the instinctive reaction is to see the length -- 670 yards! -- and recoil.

Lee Westwood, asked last month about No. 16, smiled in the understated way of an Englishman and said, "I've never been a big fan of 670-yard par-5s."

Fan or not, few players will stand on the tee and count on making birdie, their usual par-5 mindset. Ken Venturi, the San Francisco native and 1964 U.S. Open champion, flatly declared that No. 16 will be the highest-scoring par-5 in Open history.