Serena Williams takes on Lourdes Dominguez Lino today in the second round of the 2013 Mutua Madrid Open (11:30 BST start).
Serena wasn't especially convincing in her first match of the year on red clay. She came back from a break down in the first set to beat 18-year-old qualifier Yulia Putintseva, 7-6 6-1.
"Yulia and I train sometimes at the same facility, the Mouratoglou Academy in France - I see her around a lot and see her working really hard," Williams said afterwards.
"Honestly, I obviously have to - and want to - play better as each match goes on here. I felt a little sluggish out there today, but I'm happy I won."
Serena has been training in Paris ahead of the tournament.
"I've been in Europe for a little over a week; maybe a week and a half," she added.
"Not super long, but not long enough. I was training in Paris for a few days and I just came to Madrid a couple days early."
Dominguez Lino is currently ranked 47 in the world but such is the strength of this event that she required a wildcard to avoid having to go through qualifying. She made the most of it, defeating fellow wildcard Simona Halep 6-2 4-6 6-4 in the opening round.
Serena has won both their previous matches in straight sets, the last coming at Wimbledon 2007.
Prediction: Williams in two.