In the second singles, Argentina's Franco Squillari, ranked 116, beat Chile's 397-ranked Hermes Gamonal 6-2 6-4 6-2.
Cheered on by a sell-out crowd at the Buenos Aires Lawn Tennis Club, Gumy came close to pushing the pony-tailed left-hander to five sets. But Rios survived three set points on his own serve when he was down 5-4 before winning the next three games. The victory means Rios is guaranteed to keep his No 1 spot for at least three more weeks, following the withdrawal of Pete Sampras from the Hong Kong Open.
The Davis Cup holders Sweden, undermanned by injuries to their stars, dropped both singles matches on the first day against Slovakia on Friday. Dominik Hrbaty began by outlasting Magnus Norman 7-6 4-6 6-4 3-6 6-2 in a three-hour, 36-minute match that turned in the fourth game of the last set when he broke serve for a 3-1 lead.
Then the heavily fancied Karol Kucera, conqueror of Sampras, the then No 1, at the Australian Open, overcame early jitters to defeat Mikael Tillstrom 1-6 6-1 6-2 6-4.
But while the Swedes suffered, Germany gloried in the achievements of two 20-year-olds as they seized a 2-0 lead over South Africa in Bremen.
Tommy Haas celebrated his 20th birthday on his Davis Cup debut by beating Wayne Ferreira 7-6 3-6 6-3 6-4, while Nicolas Kiefer, also with no previous experience of the Davis Cup, overcame a sluggish start to tame Grant Stafford 4-6 4-6 6-1 6-2 6-2 in the opening match.
In Mildura, the ailing US Open champion Pat Rafter suffered a surprise defeat against lowly ranked Byron Black to leave Australia and Zimbabwe locked at 1-1 on the opening day of their Davis Cup tie on Friday.
Rafter, ranked fourth in the world, crashed to a 3-6 6-3 6-2 7-6 defeat against the Zimbabwean, ranked a modest 81. Jason Stoltenberg overcame Wayne Black 6-3 6-4 5-7 7-5 in the opening singles match.
The French Open champion, Gustavo Kuerten, staged a stunning recovery to overcome Carlos Moya 5-7 1-6 6-4 6-4 6-4 and give Brazil a 1-0 lead against Spain in Porto Alegre. But Alex Corretja revived Spain's hopes by overcoming Fernando Meligeni 4-6 6-4 3-6 6-4 6-4.
In Zurich, the Czech Republic were level with Switzerland 1-1. The Czech Bohdan Ulihrach beat Ivo Heuberger 6-7 (6-8) 6-0 7-5 6-2 in the first singles. Then Marc Rosset blasted 18 aces past Daniel Vacek as he hammered out a 3-6 6-2 7-6 6-0 comeback victory to square the tie for the Swiss.
Rain hampered the tie in Genoa where Italy led India 1-0 when rain stopped play for the day.
Filip Dewulf mastered winds and rain to sweep past Sjeng Schalken 7- 5, 6-2, 7-5 yesterday and pull Belgium back level with Holland 1-1 in their group match.Reuse content