Andre Agassi's achievements off the court may be more impressive than those on it. Ryan Pierse/Getty Images
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Outspoken tennis pro Justin Gimelstob will be writing every few days from the U.S. Open, where he'll be competing. Click here to read all of Justin's entries.

Professional athletes are big targets -- and when you consider all the trouble some of us get ourselves into, we almost deserve those bull's-eyes on our backs. But there are many truly good players who avoid the police blotter, and they're great role models both on and off the playing field.

I'm extremely fortunate that I've had the opportunity to see many of these guys up close during the course of my professional tennis career. But one stands above the rest: Andre Agassi, who's competing in his 20th U.S. Open this year.

Agassi has been the biggest draw in tennis for two decades now and he's the best possible ambassador -- not only for tennis, but in the entire sporting world. He continues to find ways of challenging himself to get better, all while battling Father Time and a new breed of incredibly talented players. He'll pack the house every time he plays over the fortnight, increasing television ratings and inspiring countless people to pick up their rackets and get onto the courts.

I've been lucky enough to spend some time with Andre over the years, and he is an even more impressive person up close. He has a great heart and is the most generous person I have ever come across. Andre's accomplishments through his charitable foundation are well documented and incredible in their own right (he's raised more than $50 million for underprivileged kids), but it's just as amazing to hear him talk with passion and pride about the kids whose lives he affects. Andre is a role model not just to young tennis players, but to all professional athletes -- all of whom have the ability to positively effect change in people's lives.

On a similar note, I've recently found myself in the curious position of defending two of the best tennis players in the world: Andy Roddick and Tim Henman. This is an interesting spot for me to be in, since I've never accomplished one-zillionth of what they have. I'm astonished when I hear people knocking these guys by asking, "What's wrong with Andy and Tim and why aren't they doing better?"

So the insinuation is that they're failing by being two of the best tennis players in the world?

Roddick has taken the mantle as the top-ranked American in the world for the past few years, reached the Wimbledon finals twice, won 19 singles titles and represented the U.S. Davis cup team at every opportunity -- all while maintaining a great attitude and juggling fame and all of its trappings about as well as any young guy could.

Meanwhile, Henman has had an incredible career. He has reached the Wimbledon semifinals four times and has put up with an unimaginable level of scrutiny and pressure in Great Britain. He is one of the friendliest and most popular players on tour, is a great family man, has his priorities firmly intact and conducts himself with class both on and off the court.

If these guys aren't celebrated because they aren't winning Grand Slams left and right, then maybe the barometer of success in this game is a bit too high and unrealistic.

Nice going, James

On another note, I'd like to take this opportunity to congratulate James Blake, not only for his awesome effort in winning the Pilot Pen Championships in New Haven, Conn., on Sunday, but also for his incredible comeback from illness and the loss of a great man -- his father -- last year.

James is a very special guy with so many things going for him, and it's great to see him happy, healthy and playing great tennis again. I would like him even more if I didn't have the sneaking suspicion that my girlfriend, Corina Morariu, likes him more than I do. But it's tough for me to blame her.

I also want to give props to James' longtime coach, Brian Barker. I know James was hearing a lot of whispers that he needed a new coach when he was struggling with his game over the past three years, but he believed in Brian, and now they're seeing the payoff from a lot of hard work and confidence in each other.