At the World Tour Finals of men’s tennis in London this week, eight of the world’s best doubles teams are vying for the one of the most prestigious titles of the season. Bob and Mike Bryan, the 16-time Grand Slam winners, are competing with other elite duos such as U.S. Open winners Jamie Murray and Bruno Soares and Wimbledon champions Pierre-Hugues Herbert and Nicolas Mahut.

But the field is missing one notable name: Jack Sock, the American who won two doubles medals at the Olympics over the summer in Rio. Sock’s current doubles ranking of No. 14, reached by playing with seven different partners this year, places him ahead of four players present this week in London. But Sock didn’t make the cut because inclusion in the London field is based on ranking points accumulated by teams, not individual players, and each of his short-term teams finished far out of contention.

Yet it’s likely that the official rankings drastically undervalue Sock’s doubles prowess. According to a version of Elo I created specifically for doubles tennis, his current level of play in doubles matches rates as the best in the world and one of the highest achieved by anyone in recent years. In addition to his men’s doubles bronze medal in Rio, Sock has won two titles in the past month, including an incredible run at the Shanghai Masters in which he and partner John Isner defeated four London-bound teams in succession.

Doubles Elo (D-Lo, if you will) is almost as straightforward as the singles system. The rating of any partnership is estimated as the average rating of the two players. (While there is anecdotal evidence that suggests a team improves as partners play together more often, incorporating that into the algorithm doesn’t make it any more accurate.) After every match, each of the four players’ ratings is updated by adding or dropping points based on the result and their opponents’ strength. I’m using D-Lo to forecast the doubles tournament at the World Tour Finals.

ELO RANK PLAYER AGE ELO PEAK ELO ATP RANK 1 Jack Sock 24 2002 2022 14 2 Pierre Hugues Herbert 25 1995 2047 2 3 Nicolas Mahut 34 1967 1987 1 4 Bob Bryan 38 1925 2076 5 5 Mike Bryan 38 1921 2076 5 6 Henri Kontinen 26 1920 1920 10 — Rafael Nadal 30 1904 1904 130 7 Marcelo Melo 33 1896 1983 7 8 Ivan Dodig 31 1874 1924 11 10 John Peers 28 1865 1888 12 12 Jamie Murray 30 1859 1899 4 14 Marc Lopez 34 1846 1933 8 15 Bruno Soares 34 1843 1955 3 21 Raven Klaasen 34 1824 1917 16 22 Feliciano Lopez 35 1814 1845 9 — Roger Federer 35 1785 1921 — 28 Rajeev Ram 32 1776 1825 17 34 Max Mirnyi 39 1763 2010 21 — Andy Murray 29 1757 1818 259 41 Treat Huey 31 1740 1866 22 — Novak Djokovic 29 1668 1726 — The World Tour Finals doubles field and other notable players To have a current Elo rank, players need to have played at least 20 matches this year. Source: Tennisabstract.com, ATP World Tour

Sock is missing from the London field largely by choice. In July, he said he would compete in fewer doubles events in order to better focus on his singles career — he ranks No. 23 in singles, near his career high. He ended his partnership with Vasek Pospisil, the Canadian with whom he won the 2014 Wimbledon title, and skipped the doubles event at this year’s U.S. Open. Since September, he has played four events with four different partners — hardly the behavior of a would-be elite doubles player.

The American is hardly alone in his decision to prioritize singles. Doubles players perform far out of the spotlight, rarely netting the press and prestige of their singles-playing counterparts. What’s more, the top doubles players each earn about one-tenth the prize money that top singles players make. Plenty of elite singles players are accomplished on the doubles court — Roger Federer and Rafael Nadal both won Olympics doubles gold medals — but most usually elect to rest rather than play doubles for a lesser prize pool and a smaller fraction of the acclaim. Of the 16 doubles players in London, only Feliciano Lopez and Max Mirnyi have ever numbered among the top 20 on the singles ranking table, and for 39-year-old Mirnyi, that was 13 years ago.

SEED TEAM (PLAYER 1/PLAYER 2) PLAYER 1 ELO PLAYER 2 ELO TEAM ELO (AVG.) 1 Pierre-Hugues Herbert/Nicolas Mahut 1995 1967 1981.0 2 Jamie Murray/Bruno Soares 1859 1843 1851.0 3 Bob Bryan/Mike Bryan 1925 1921 1923.0 4 Feliciano Lopez/Marc Lopez 1814 1846 1830.0 5 Henri Kontinen/John Peers 1920 1865 1892.5 6 Ivan Dodig/Marcelo Melo 1874 1896 1885.0 7 Raven Klaasen/Rajeev Ram 1824 1776 1800.0 8 Treat Huey/Max Mirnyi 1740 1763 1751.5 Jack Sock/Vasek Pospisil 2002 1830 1916.0 The eight World Tour Finals teams and Sock/Pospisil Source: TennisAbstract.com

Despite his priorities, Sock would have been a force to reckon with in London. A pairing with Pospisil would, as measured by Elo, outrank every team except for Herbert-Mahut and the Bryans. Even a partnership with Steve Johnson — Sock’s fellow bronze medalist and a lowly 56th on the Elo ranking table — would be the fifth-rated team at the finals.

If he remains focused on singles and resists sticking with a steady doubles partner, Sock could still be a factor in future editions of the season-ending doubles event. The average age of the doubles participants in London this year is 33, while Sock is 24. According to Elo, the Bryans didn’t reach their peak until close to their 30th birthdays, and Mahut, at age 34, is having the best doubles season of his career. For most players, it would be a career-defining achievement to reach Sock’s current level of doubles skill. For the American, he has another decade to decide if it’s worth it.