This post is part of a series on celebrity spokespeople who ended up doing serious harm to the brands they were hired to promote, or vice versa. See how we rank the 20 top spokesperson fiascos.

By guest blogger Mike Brewster:

Former women's number one Martina Hingis hung up her tennis shoes for good last year after testing positive for cocaine in a post-match drug test -- within the hallowed confines of the All England Club Lawn Tennis and Croquet Club (that's Wimbledon to you and me, pal), no less.

At one point Hingis' career was on a Chris Evert/Martina Navratilova-type trajectory, but got derailed by a slew of injuries that started in the late 1990s. The main culprit was a chronic foot problem she always maintained was caused by defective sneakers from her Italian sports apparel sponsor, Sergio Tacchini.

In 2001, Hingis filed a $40 million lawsuit against the company, claiming that the sneakers, which she wore from 1996 through 1999 as part of a $5.6 million endorsement deal, "were unsuitable for competition." Sergio Tacchini fired Hingis that same year as its main celebrity endorser.

Even though the Manhattan Supreme Court dismissed the suit in November 2002, the company never really recovered. The brand that once clothed John McEnroe, Jimmy Connors and Pete Sampras filed for bankruptcy last year, and just last month its remaining assets were purchased by Hong Kong businessman Billy Ngok. And as we all know, these days nothing says "quality athletic shoes" like Chinese manufacturing.

Read the entire series