Aside from the four Grand Slams, the Davis Cup is the other internationally popular event during the tennis calendar. The men’s event, which has existed since 1900, uses a multi-tiered system that pits country against country. While Spain won last year, the United States has won the event a record 32 times.

Unfortunately, both Rafael Nadal and Roger Federer, the #1 and #2-ranked players on the men’s tour, have dropped out of the competition due to injury.

Roger Federer pulled out of Switzerland’s Davis Cup series against the United States next month and a tournament in Dubai next week because of a back problem that has bothered him since last year.

“As a precautionary measure, I will use the next few weeks to make sure the back injury is fully rehabilitated and I am ready for the rest of the 2009 season,” Federer said in a statement posted on his Web site Tuesday.

He has not played a competitive match since Feb. 1, when he lost to top-ranked Rafael Nadal in five sets in the Australian Open final. A victory over Nadal in that match would have allowed Federer to tie Pete Sampras’ career record of 14 majors.

A right leg injury could force Nadal to miss the Feb. 23-28 Dubai tournament, too, but he said Monday he hopes to play for Spain in the Davis Cup.

“This was a hard decision to make as I am missing not only one of my favorite events on tour in Dubai, but I am also missing out on an opportunity to help my country try and move on to the next round of Davis Cup,” Federer said.

I wonder if both Federer and Nadal are using this time to rest up and squeeze in some extra training before the French Open in May. The Australian Open could not have been any better for tennis, so I hope both of these guys are back to their full strength before the Grand Slam at Roland Garros.

The Davis Cup is a fairly big deal worldwide. It’s a shame that it never gets much attention in the U.S., especially since we tend to win the tournament quite often. With Nadal and Federer out, there will be even less an incentive for people to watch.

The first round of the Davis Cup will take place on March 6-8 in Birmingham, Alabama.