Maria Sharapova rallies, advances
The second-seeded Russian said she was still adjusting to changing weather conditions in Madrid and "the altitude as well" after winning the title in Stuttgart last weekend. Madrid is 2,180 feet above sea level.
"It was a tough match," Sharapova said. "I was really happy that I got that break back in the first set and was able to win in two sets."
Azarenka, who finished runner-up in Madrid the past two years, is returning from an ankle injury and said it was good to get a tough test right away.
"I don't think I could have asked for a better match to start after a break," she said.
The third-ranked Azarenka broke to go up 4-3 in the first set before Pavlyuchenkova broke back. Azarenka then saved three set points at 6-3 down in the tiebreaker.
"When you don't play so much, you kind of lose that momentum," she said. "In the tiebreak, I just tried to find my game to find the solution to make things happen for me."
The 19-year-old Robson arrived in Spain coming off her sixth first-round loss of the year at the Portugal Open but was able to capitalize on her break points against last year's Wimbledon finalist.