The US Open, the final major championship of the tennis season, doesn’t start until a week from Monday in New York, but there was some big news this week that certainly will affect who wins the men’s singles title on Sept. 9 (always one of the best days of the sports calendar is the men’s final and the opening Sunday of the NFL season occurring on the same day).

Rafael Nadal, the reigning French Open champion, will miss the hard-court tournament with a knee problem that has plagued him off and on for years. Many believe that Nadal was bounced out of Wimbledon in the second round because of that knee, which also forced him to skip the Olympics – he won gold in the 2008 Games -- and the recent hard-court US Open tune-up tournaments in Toronto and Cincinnati.

The 26-year-old former No. 1 player is now down to No. 3. Nadal’s win at the French was his record seventh there and 11th career Slam title. He had competed in the US Open every year since 2003 and won his lone title there by beating Novak Djokovic in four sets in 2010. That capped a career Grand Slam for Nadal. Last year he lost to Djokovic in a four-set final.

It’s time to wonder if Nadal will ever be the same with those knees. His all-out style of play takes a huge a toll on his body, particularly his knees. He was also forced to withdraw from Wimbledon in 2009 as the defending champion because of the knees. Nadal is hoping to play in the Davis Cup semifinal against the USA next month, but I’d be surprised if he’s back in 2012.

All of the top contenders’ odds changed a bit with Nadal’s W/D. Djokovic is the current 3/2 favorite at Bovada. The hard courts are easily Djokovic’s best surface. Four of his five Grand Slam titles have come on the hard courts, three Australian Opens and last year’s US Open.

Djokovic came up short this season at the French, losing to Nadal in the final, and then losing to Roger Federer in the semis at Wimbledon, which is when Djokovic lost his No. 1 ranking to Federer. Djokovic also was beaten twice in the Olympics, in the semis by Andy Murray and in the bronze medal match by Juan Martin del Potro. But the Serb has looked rejuvenated in the hard-court tune-ups and has reached at least the semifinals in the past five US Opens, with two runner-ups to go with that victory.

The rejuvenated Federer is the 11/4 second-favorite. The Swiss star won his record-tying seventh Wimbledon for his 17th career Slam but first since the 2010 Australian Open. Federer is 17-7 overall in Slam finals in his career. That record is 5-1 at the US Open. Federer had won five straight before being stunned by del Potro in 2009. Federer has been ousted in the semis the past two years. One almost has to expect a Djokovic-Federer final. While Federer leads 15-12 overall, Djokovic beat him in last year’s semis to go 4-0 on hard courts vs. Federer in 2011. But then Djokovic was practically unbeatable last year and isn’t the same player in 2012.

Realistically, the only other player worth betting on to win is Andy Murray at 3/1. He remains without a Grand Slam title after losing in the finals at Wimbledon to fall to 0-4 all-time in Slam finals. Murray did get a bit of a monkey off his back by thrashing Federer in the gold medal match in London. But Murray was routed by unheralded Jeremy Chardy at the Western & Southern Open in Cincinnati on Thursday. Murray had easily handled Chardy in their previous four matches. In addition, Murray had to withdraw from the Toronto tune-up because of some knee pain.

My pick here is Federer because you know he’s going to reach at least the semifinals. I’m not confident in saying that about either Djokovic or Murray right now.

On the ladies’ side, a rampaging Serena Williams is the even-money favorite. Serena destroyed everyone at Wimbledon and then did the same at the Olympics, dropping a total of 17 games in six matches. It was almost hard to watch Serena’s 6-0, 6-1 win over Maria Sharapova in the gold medal match because of how overmatched Sharapova was. Sharapova has lost her past eight matches to Williams, a streak that goes back seven years.

The only chink in the armor is that Serena hasn’t won the US Open since 2008, her third overall title there. Williams was a heavy favorite in last year’s final against Aussie Samantha Stosur but was beaten, 6-2, 6-3. You may remember that match. Down a set and facing a break point in the first game of the second, Serena hit a forehand and shouted, "Come on!" as Stosur reached down for a backhand. The chair umpire ruled that Williams hindered Stosur's ability to complete the point and awarded it to Stosur -- putting her ahead 1-0 in that set. Serena then loudly berated the umpire. There’s something about the US Open that brings out the worst in Williams. In her 2009 semifinal loss against Kim Clijsters, Serena was called for a foot-fault that set her off on a profanity-laced outburst at a line judge. Williams lost a point there – it came on match point.

The only player I would bother putting money on other than Serena is Clijsters (16/1), who will retire after this tournament. Clijsters originally retired in 2007 before the birth of her daughter but returned in 2009 and went on to win the US Open that year and in 2010 (also in 2005). She didn’t get a chance for a three-peat in 2011 as Clijsters had to pull out injured. The 29-year-old Belgian clearly likes the hard courts as she also won an Australian Open crown in 2011.

Clijsters has played in only three majors since then due to injuries, with a best finish of the semifinals at this year’s Aussie. It would be a great story if Clijsters, who has no titles in 2012, could go out on top, and I think she can if she can avoid Serena in the draw.