What are the 10 greatest records and achievements during the past decade? Check out our picks and see why Roger Federer and Rafael Nadal dominate the list.

1. Roger Federer’s dominance at Grand Slam level was the most significant achievement of the first decade of the new century. During the decade Federer became the only player in history to win five straight titles at two Grand Slam tournaments, dominating Wimbledon from 2003-07 and the US Open between 2004-08. The Swiss also became the only man to reach all four Slam finals in the same year three times. When Federer won the 2009 Roland Garros title he became just the sixth man in history to complete a career Grand Slam. Federer has reached 22 consecutive Grand Slam semi-finals, more than double the length of the next-best Open Era streak (Ivan Lendl’s 10 straight semi-finals).

2. Roger Federer was crowned ATP World Tour Champion five times during the decade, tying Jimmy Connors’ five finishes as year-end No. 1 in the South African Airways ATP Rankings and edging to within one of Pete Sampras’ six (consecutive) No. 1 finishes. Federer set a record for most consecutive weeks at No. 1 (237) and will end 2009 on 263 (non consecutive) weeks in the top spot, within 23 weeks of Sampras’ all-time record of 286 weeks.

3. Rafael Nadal’s four consecutive Roland Garros titles is a stunning feat. The Spaniard won on debut in 2005 and won 31 consecutive matches before big-hitting Swede Robin Soderling upset him in a fourth-set tie-break in the fourth round this year.

4. Roger Federer’s 24 consecutive victories in finals he played between late 2003 and late 2005 is a record that is likely to stand the test of time. Federer’s streak was finally broken by David Nalbandian in the final of Tennis Masters Cup in 2005, when Nalbandian rallied from two sets down to beat Federer in a fifth-set tie-break.

5. Rafael Nadal became the first man since Bjorn Borg 28 years before him to claim the elusive Roland Garros-Wimbledon double in 2008. (Federer repeated the feat in 2009). In a banner year Nadal also won Olympic gold that season.

6. Andre Agassi, at 33, became the oldest player to hold the No. 1 South African Airways ATP Ranking in 2003. Agassi’s feats of longevity were an inspiration during the decade. In the decade he won 16 titles, including three Australian Opens (at age 29, 30 and 32) and a 17th ATP World Tour Masters 1000 title in Cincinnati as a 34 year old.

7. Roger Federer’s 173-9 match record in 2005-06 makes our Top 10 list. Federer produced unrivaled back-to-back seasons of brilliance in the middle of the decade. He went 81-4 in 2005 and 92-5 in ’06, winning 23 titles during that span, including five Grand slam titles and eight ATP World Tour Masters 1000 crowns.

8. Rafael Nadal’s imposing clay-court streak during the decade was breathtaking. Nadal, who owns a 181-16 career win-loss record on clay, won more than 11 matches for each one he lost on the surface. He amassed an 81-match winning streak between 2005-07. His record in best-of-five-set matches on clay is 49-1 and he has won 24 of 26 finals on the surface.

9. Lleyton Hewitt is the only man other than Federer to be crowned ATP World Tour Champion two straight years during the decade: in 2001 when he won the US Open and Tennis Masters Cup (now Barclays ATP World Tour Finals) and in 2002 when he Wimbledon and Tennis Masters Cup. Hewitt held the No.1 South African Airways ATP Ranking for 75 consecutive weeks – including for the entire 2002 season – and 80 weeks in total. Hewitt remains the youngest player (at 20 years, 8 months) to be crowned ATP World Tour Champion.

10. Rafael Nadal‘s record at ATP World Tour Masters 1000 tournaments is astonishing. Before turning 23 in June, Nadal had won 15 of the ATP World Tour’s premier tournaments between 2005-09. He trails Federer by just one and all-time leader Agassi by two titles. (Agassi won his record 17th ATP World Tour Masters 1000 title as a 34 year old.)

Honorable Mentions

Gustavo Kuerten became the first Brazilian to be crowned ATP World Tour Champion at a dramatic Tennis Masters Cup in Lisbon in 2000. Kuerten did what no other player had previously done – beaten Agassi and Sampras back-to-back in the semi-finals and final – to win the title and lock up the year-end No. 1 South African Airways ATP Ranking.

Nicolas Massu winning singles and doubles gold at the 2004 Olympics.

Roger Federer’s 65-match grass-court winning streak beginning in Halle in 2003 and ending with his 2008 Wimbledon final loss to Nadal may never be equaled, given the short grass-court season.

Rafael Nadal reaching 400 match wins faster than any other active player is worthy of note. Nadal reached his 400th win from 491 matches, topping Federer and Hewitt, who both needed 520 matches to register their 400th wins.