Monday marked the 161st week that Federer has been ranked No. 1, passing the record set by Jimmy Connors from July 29, 1974 until Aug. 22, 1977. Federer has been world No. 1 since Feb. 2, 2004.
Monday also marked the first return to play for Federer, 25, since he won the Australian Open. He ran his personal winning streak to 37 matches but showed some rust as he slipped past Kristian Pless, 7-6 (7-2), 3-6, 6-3. The second set marked the first lost set of the year for Federer.
In other first-round matches in Dubai, Fabrice Santoro knocked out fourth-seeded Tommy Robredo, 7-6 (8-6), 6-4, and sixth-seeded Tomas Berdych rallied for a 3-6, 6-3, 6-2 win over Mohammed Al Ghareeb. Other winners Monday were Olivier Rochus, Florent Serra, Dominik Hrbaty and Igor Andreev.
The tournament continues through the week with the eventual winner taking home $300,000.
Celebrity Families of 2014 [PHOTOS]