ASTANA, Kazakhstan — Last year's Davis Cup champion Argentina was knocked out of the competition's top tier Sunday with defeat to Kazakhstan.

Mikhail Kukushkin defeated Diego Schwartzman 6-4, 6-4, 7-6 (2) in a battle between the teams' top-ranked players to give Kazakhstan an unassailable 3-1 lead in the best-of-five match in Central Asia.

Schwartzman, who as the 28th-ranked player is 50 places above Kukushkin, lost his first two service games in each of the first two sets and struggled to recover.

Argentina — which didn't have its top-ranked player Juan Martin del Potro in Kazakhstan — is the first reigning Davis Cup champion to be relegated since Sweden in 1999.

Argentina was last outside the top-tier World Group in 2001, while Kazakhstan returns following relegation last year.