Nadal defeated Philipp Kohlschreiber 6-4, 7-5 (7-3) in a match tighter than most in the Kohlschreiber-Nadal series, now led by Nadal 11-1.
The players traded two breaks each in the early going but Nadal was able to convert for a third and take the first set. Nadal didn't have a break chance in the second set but Kohlschreiber was unable to finish off any of his three opportunities, forcing the tiebreaker.
Nadal took five straight points for a 6-2 tiebreaker lead and finished off the match two points later.
Nadal, second in the rankings and most recently No. 1 on July 3, 2011, will return to the top spot in the rankings if current No. 1 Novak Djokovic fails to defend his China Open title or, even if Djokovic wins the tournament, Nadal advances to the finals.
His next hurdle toward that goal is Fabio Fognini, who routed Lleyton Hewitt 6-0, 6-2 behind six breaks. Fognini took 60 percent of the points on serve, dropping the only break point he faced, and 61 percent off Hewitt's serve.
Also in the second round Wednesday, No. 8-seeded John Isner beat Roberto Bautista Agut 6-2, 6-7 (3-7), 6-4. Isner fired off 24 aces and lost just 17 points in 15 games serving.