42

Number of times Djokovic and Federer will have locked horns after Sunday, which moves them past Federer and Nadal (33), Connors and McEnroe (34), Connors-Lendl / Becker-Edberg (35) and Lendl-McEnroe (36) for second-most head-to-head meetings by two players. After meeting five times in 2014 and already five times in 2015 the pair are inching closer to Djokovic-Nadal.

Here are the top seven:

1. Djokovic-Nadal, 44
2. Federer-Djokovic, 42
3. Lendl-McEnroe, 36
4. Connors-Lendl, 35
4. Becker-Edberg, 35
5. Connors-McEnroe, 34
5. Agassi-Sampras, 34
6. Federer-Nadal, 33

21-20

On the strength of a 3-2 record vs. Federer in 2015, Djokovic holds the slight edge in the all-time head-to-head.

26

Grand Slam titles between the two. Federer comes in with a pretty hefty edge of 17-9. Go ahead and relive some of the glory of their 2015 Wimbledon final, you know you want to:

9-6

Djokovic owns the edge in career finals vs. Federer. Novak has won three of five this year, including the Wimbledon final. Federer won their last final three weeks ago in Cincinnati. The Swiss owns a 2-1 edge in hard-court finals this year, and they rivals have split 12 hard-court finals, lifetime.

141

Career ATP titles between the two. Federer, five years Djokovic's senior, has the edge of 87 to 54. Djokovic has six titles in 2015; Federer, 5.

465

Number of total weeks at No. 1 between the two. Federer has most all-time with 302, while Djokovic is fifth all-time with 163.

134-19

The combined record of the pair at the U.S. Open. Federer is 78-10 and if he wins the final he will own the best Open Era winning percentage of all-time. Djokovic is 56-9.

39

The number of times a Big Four (Federer, Djokovic, Nadal, Murray) member has won the title in the last 43 majors (including this U.S. Open). The only players to break through during this 43-event span are Juan Martin del Potro (2009, US Open), Stan Wawrinka (2014, Australian Open, 2015 Roland Garros) and Marin Cilic (2014 US Open).

12-5

Djokovic's record against Federer in deciding sets, including victories in seven of the eight deciders.

33-8

Record of player who wins the first set when Federer and Djokovic play. Federer is only 20-7 when taking the first set against Djokovic, far from a lock. Djokovic is 13-1 when he takes the opener.

3-2

Federer's record vs. Djokovic at the US Open. The Swiss has held match points in all five meetings but Djokovic famously came back to win their last two meetings in New York.

22

Number of tiebreakers the pair have played, with Federer owning the 12-10 edge, including three of the last four.

6

Number of US Open titles, combined, that the pair own. Federer won five straight from 2004 to 2008, and owns a 5-1 all-time record in US Open finals. Federer has not reached a US Open final since falling to Juan Martin del Potro in five sets in 2009. Djokovic owns a 1-4 record in US Open finals, winning the title in 2011, and dropping finals in 2007, 2010, 2012 and 2013.