As one of Mexico's most experienced sports journalists, Sainz has interviewed, among others, tennis players Roger Federer and Rafael Nadal, basketball players Kobe Bryant and Shaquille O'Neal, baseball players Derek Jeter and Alex Rodriguez and association football players Ronaldo, Roberto Carlos, Rivaldo, Zinedine Zidane, and Lionel Messi. By July 2006, Sainz had covered three Champions League tournaments and four NBA Finals, the 2004 Athens Olympics and the 2006 World Cup. As of 2009, Sainz had covered six Super Bowls, the first, Super Bowl XXXVI in 2002. In January 2009, promoting American football stars to a Mexican audience, Sainz ran an informal biceps competition during the Super Bowl XLIII "media day," awarding her "Strongest Right Arm" award to the Arizona Cardinals' defensive end Antonio Smith.According to the Palm Beach Post, at the 2007 Super Bowl's "media day," Sainz was photographed as often as Peyton Manning; and according to The Daily Telegraph, she was "besides Manning, the single-most popular person on the premises." During a period when Terrell Owens was not speaking with the press in 2008, it was only Sainz who was able to gain an exclusive interview with the wide receiver. In 2010, media reported that while Sainz was waiting to conduct an interview with Mark Sanchez in the New York Jets locker room, team members made "catcalls and rude comments". According to Sainz, it was "the rest of the media start to hear the different kind of things that I didn't hear."
Boxing promotion company Top Rank hired Sainz to conduct pre-event reports and interviews and offer ringside commentary for the Manny Pacquiao vs. Antonio Margarito World Super Welterweight Championship bout in Arlington, Texas on November 13, 2010. Sainz co-hosted broadcast commentary for the March 12, 2011 Miguel Cotto vs. Ricardo Mayorga bout.
