"Very weird. I mean, I just completely lost rhythm, everything. Unfortunately today I am still not strong enough", he wrote.
These two have played four times and Federer has won three of those matches.
His third-round opponent is Argentina's Leonardo Mayer, who had been scheduled to play Kei Nishikori in the second round before the world No. 25 withdrew through illness. We wait, we play, we wait again, we play again.
After the shock early exit from the the BNP Paribas Open, former world number one Novak Djokovic admitted he felt like he was playing his first match on tour on Monday.
"I think I came out playing a little more aggressive than the other two sets and that made him keep making more mistakes".
"At the Masters 1000s, when the format was different, it was the best-of-five-set finals in the finals".
Holder Roger Federer avoided the same fate as Djokovic, though the Swiss top seed was pushed by left-handed Argentine Federico Delbonis in a match that was completed on Sunday after being halted by rain at 2-2 in the second set the previous day.
Israeli Dudi Sela beat British 21st-seeded Briton Kyle Edmund 6-4 6-4 while Luxemburg's 24th seed Giles Muller was upset by Frenchman Pierre-Hugues Herbert 6-3 7-5.
Stephens lost to Daria Kasatkina of Russian Federation 6-4, 6-3, and fell to 2-4 in matches this year.
Also, American Taylor Fritz defeated Fernando Verdasco of Spain, 4-6, 6-2, 7-6 (7/1), Croatia's Borna Coric breezed past Roberto Bautista 6-1, 6-3 and Pablo Carreno-Busta of Spain, stopped Russian Daniil Medvedev 6-1, 7-5. Likewise, 23rd-seeded Hyeon Chung of South Korea dispatched 12th-seeded Tomas Berdych of Czech Republic 6-4, 6-4, despite 12 aces against just one double fault from Berdych.