Fish approaching major milestone

KEY BISCAYNE, Fla. -- Mardy Fish would be the perfect spokesman for all the ailments that visit men of a certain age.

Coming into the Sony Ericsson Open, he had recently struggled with a cranky knee, a sprained ankle and a dangerously rampant thyroid condition that kept him off the practice court at Indian Wells for six days. On Tuesday, his calf started cramping in the brutally humid conditions.

"I've done my fair share of blood work in the past couple months, every four or five days, and the levels are very far down," Fish observed Sunday.

This is contrary to Fish himself, who at the advanced age of 29 is playing -- contrary to the norm -- at the highest level of his life. He took down the ever-improving Juan Martin del Potro 7-5, 7-6 (5) to advance to the quarterfinals, in which he'll play David Ferrer on Wednesday.

Del Potro, still trying to find the form of a Grand Slam champion after missing nine months following wrist surgery, was suffering from a leg injury that may delay the start of his clay-court season.

In his 12 seasons as a professional, Fish has never been America's top player. First it was Pete Sampras, then Andre Agassi, then Andy Roddick and, for one year, 2006, James Blake. If Fish can beat the relentless Ferrer -- hardly a stretch, even on these slow hard courts -- he would reach the semifinals and become the top-ranked U.S. player, somewhere around a career-high No. 12.

With a trip to the final, Fish probably would find himself ranked in the ATP top 10.

Each time the subject comes up, Fish has deferred to his close friend Roddick. On Tuesday, he did it again.

"You just kind of feel like coming through with Andy and the career that he's put together, you really feel like it would probably be pretty tough to still feel like I was the No. 1 American," Fish said. "His career put on my career, he could put it on top of mine 15 times. He's won so many more matches, so many more tournaments, so many more Davis Cup matches.

"So I don't think I would ever feel like the No. 1, even though, if I were to win tomorrow, the number next to my name would be smaller than his."

This reverse-aging thing goes against all logic. How did it happen?

Coach David Nainkin, who has been working with Fish under the auspices of the USTA for the past two years, traces Fish's turnaround to November 2009, when he underwent knee surgery and made the decision to fully commit himself to the game.

"Sometimes guys late in their careers start figuring it out," Nainkin said. "Mardy changed his eating habits and his approach to fitness, changed his whole outlook to give himself a full shot.

"With his new fitness level he's able to play defensive tennis now. He can pick and choose his opportunities to come in, so it's high-percentage tennis, and he can still be aggressive."

In gaining a few feet of range in the narrow confines of the court, Fish now finds himself in rallies long enough to win them. Like Andrea Petkovic, who picked her spots in beating world No. 1 Caroline Wozniacki on Monday, Fish stayed in points, and when the short ball came from del Potro, he ripped at it. This also leads to unforced errors, but it's a risk-reward ratio Fish can live with.

Fish created a number of openings for himself but failed to cash any of those chips for the longest time. Finally, with del Potro serving to reach a tiebreaker, Fish broke through on his sixth set point. Better lucky than good; his backhand clipped the net and dropped in.

The second set looked much the same, but with del Potro winning at 5-6 to force a tiebreaker. Fish fashioned a 5-0 lead with some big serves and a del Potro double fault but again struggled to close it. At 6-5 (there's that score again), he converted his third match point when a weary del Potro service return strayed long.

Fish, who looked pretty beat himself after 2 hours, 25 minutes on court, stood still on the baseline and raised his arms. He hugged del Potro, with whom he has played doubles (and will again this year in Madrid), warmly at net. The animated crowd, pro-del Potro throughout the match, applauded more than politely.

"I didn't know where I was," joked Fish, who grew up in South Florida.

He has told the story of his midlife crisis, his transformation many times. He is always careful to credit his trainer, Christian LoCascio, and speak in terms of "we," not just "I."

Fish's defining knee injury, he said, "was for lack of work ethic. It was for lack of discipline, not being a true professional in every sense of the word. That was me, an immature person."

Today, although he sometimes "cheats" -- out of competition -- with a glass of wine or a slice of strictly cheese pizza, Fish has evolved into the consummate professional.

"As a male athlete at 29, you're in your prime," Nainkin said. "I think he has a lot of good years left."

Earlier Tuesday, a Chinese journalist had asked whether Fish was a common last name in America.

"It makes for good titles," he said, "even in China."

Indeed, Fish has always been a favorite of headline writers, who have often found a negative connotation in the name, which is, let's be honest, sort of fishy. A few classics: Grilled Fish, Fish out of Water, Gone Fishin' and, of course, Dead Fish.

Well, it's time to change the karma. To celebrate his possible ascension to the country's No. 1 spot, may we suggest: Flying Fish?

Near the end of his news conference, Fish finally gave us a glimmer of what being the top American might mean to him.

"It means that the hard work that we have put in is paying off," he said. "I have never been past the quarterfinals of a Grand Slam. Apart from that, I've played a lot of big matches. Played a Davis Cup final match, Masters Series finals, and you just try to, when it's all said and done, you're going to want to try to be in every position possible.

"Being the No. 1 American would be something that would be pretty cool to tell my kids about."

Greg Garber is a senior writer for ESPN.com.