KEY BISCAYNE, Fla. -- The announcement that Novak Djokovic's postmatch news conference would be delayed because he was visiting with the Sony Ericsson Open doctor created sighs and a few wisecracks in the teeming media room on Wednesday.
The 21-year-old Serbian tends toward the theatrical and, after a deceptively wrenching 6-3, 6-4 victory over Jo-Wilfried Tsonga in this heat and humidity, it wasn't exactly astonishing he would require extra attention.
"I've been not feeling well with the stomach last night and this morning," Djokovic reported. "And probably the heat affected as well, combined, of course, with the pressure on the court and all these things.
"But, look, it's just incredible the way I stood up and tried to survive out there on the court."
Tsonga was the only player ranked outside of the top nine to reach the quarterfinals here at the Sony Ericsson Open, but he had very much had Djokovic's number since losing to him in the final of the 2008 Australian Open. In fact, Tsonga, 23, had won four straight.
"I have to be very happy with today's performance because I have been struggling to find a way to win against him," Djokovic said. "It was all so close, so I just knew that I need to stick in and try to wait for my chances and be aggressive.
"In the last couple of matches we've played, I was just -- for no reason -- waiting for him to make shots or the mistakes. Today, I tried to be closer to the line, more in control, just put the pressure on him."
This was good news for Djokovic, who recently has been in search of anything remotely positive. Ranked No. 3 but in danger of losing his bronze position to the rising Andy Murray, he has already lost seven matches this year.
"Look, I'm really happy that the people don't talk about me now," Djokovic said last week. "It releases pressure and then I can really perform my best tennis. So I think it goes to my favor."
Tsonga is ranked No. 11 and was serving better than anyone entering the match. He had won all of his 33 service games, but Djokovic broke him twice and Tsonga failed in all five of his break chances. In the eighth game of the second set, Tsonga had numerous chances to level the set but failed -- after nearly 15 minutes.
Djokovic, who won this tournament in 2007, gets the winner of late Wednesday night's Roger Federer-Andy Roddick match, which will surely test his wavering confidence. He has already lost twice to Roddick in three months, most recently a 3-6, 2-6 quarterfinal match at Indian Wells that Djokovic called "one of the worst matches I've played in my career on this surface."
He elaborated when he arrived here in Miami.
"That day and that match I wouldn't like to remember, of course, but you always try to learn from your mistakes," Djokovic said. "I didn't do a great job at all.
"I don't think it's specifically any shots, forehand, backhand, serve. Just in general, mentally that day I wasn't there. I think that's what I need to really prove to myself, that I have quality, enough quality that I can be one of the best players in the world.
"I just need to be confident."
Given the looming opponent, that won't be easy.
"I didn't really give [Roddick] a tough time on the court," Djokovic said. "I have to change some things if I play him. He's a big server. We all know that he loves playing in the States, and this is where he makes his biggest impact.
"On the other hand, Roger, there's not much to talk about him. He's so consistent in the major events. He's been so dominant the last couple of years. Tough, tough encounter against the both of them."
Confidence. This is the currency of professional tennis -- or any other sport, for that matter. Djokovic has an opportunity to regain it in large measure with a win in Friday's semifinal.
Greg Garber is a senior writer for ESPN.com.