Rafael Nadal clinches year-end No. 1 and advances to Tour Finals semis

Rafael Nadal last finished the season atop the rankings in 2010. (Clive Brunskill/Getty Images)

LONDON -- Rafael Nadal defeated Stanislas Wawrinka 7-6 (5), 7-6 (6) on Wednesday in round-robin play at the ATP World Tour Finals, securing his spot in the semifinals and locking up the year-end No. 1 ranking for the third time in his career.

"[It is] one of the best things that I did in my career -- come back to No. 1 after three seasons," said Nadal, who also finished No. 1 in 2008 and 2010. "That's very difficult in our sport ... [and] that's an emotional thing for me."

Nadal became the first player to finish No. 1 three years after his last No. 1 year-end ranking and just the third player to finish No. 1 after relinquishing the top spot. The 27-year-old Spaniard accomplished the feat despite missing the Australian Open and beginning his season in February after being out seven months with a knee injury.

Nadal was ranked fifth when he made his 2013 debut at the VTR Open, where he lost in the finals. The following week, he won the Brasil Open, jump-starting his incredible season. In 16 completed tournaments, Nadal has made 13 finals and won 10 titles.

He stormed to his eighth French Open title this year and won his second U.S. Open title, defeating then-No. 1 Novak Djokovic along the way each time. With Wednesday's victory, Nadal improved to 73-6 in 2013 and inched closer to his first World Tour Finals title.

"After all the success I had during the season, winning five Masters 1000s, playing a final in another, winning a few ATP 500s, playing another final, winning two Grand Slams ... I felt I deserved to be here at the end of the season," Nadal said.