KEY BISCAYNE, Fla. -- Canadian Daniel Nestor and Serbian partner Nenad Zimonjic lost 6-4, 7-6(4) to Americans Jack Sock and Ryan Harrison in a men's doubles quarterfinal at the Sony Open on Wednesday.
The young American pair put out the match-tough, sixth-seeded veterans in 73 minutes as Nestor and Zimonjic let opportunities slip.
Nestor suffered disappointment at the tournament for a second consecutive year following an exit in the 2013 second round. Nestor and former partner Max Mirnyi played in the final at the event in 2011 and 2012.
Nestor, from Toronto, won the 2002 title with Mark Knowles of the Bahamas.
Zimonjic began the match well enough with a love game but also lost his serve in the ninth game as Sock and Harrison took a 5-4 lead before serving out the first set in 27 minutes.
The second set went into a tiebreaker as Nestor and Zimonjic tried to recover only to go down to the loss.
"There were some service games in the first set where we gave them too many chances," Nestor said. "We didn't do a lot and they took advantage.
"There are days like this when you don't come out sharp or the other guys start getting more confidence and go for their shots more.
"They were playing well today. All opponent are tough, we knew what to expect. But some days you are mentally sharp and ready to play -- other days not so much, like today."
Nestor will next play on clay at Monte Carlo in mid-April.