Beckham, whose 10-year marketing relationship with Pepsi recently ended, came to the United States in 2007 in a much-hyped deal with Major League Soccer worth up to $250 million (£164 million). His addition was meant to increase America's affinity for the sport and the league.
"Becks" was already an international star for his play on the field overseas, good looks and marriage to former Spice Girl pop star Victoria "Posh Spice" Adams. But his U.S. tenure has been marred by injury and poor performance by his Los Angeles Galaxy team, and MLS TV ratings remain stagnant.
"He is no longer a world-class athlete, and therefore has become less interesting to some companies," said Stephanus Tekle, senior consultant at global sports marketing consultancy SPORT+MARKT in Cologne, Germany.
Shortly after Beckham, 33, came to America, he split with Procter & Gamble's Gillette brand. Now he may find it even harder to attract new sponsorships.
Some marketing executives note, however, that Beckham's popularity is more than most athletes can boast, making it harder for advertisers to replace him.
"Has he lost a little bit of the icon status he may have had five years, six years ago? I think so, but that's also a natural progression in the career of most celebrities," said Matt Delzell, senior client manager with Davie Brown Talent, an Omnicom Group unit. "He certainly is still very recognizable globally."
Beckham's current endorsements include deals with U.S. handset maker Motorola, German sporting goods giant Adidas AG, Newell Rubbermaid's Sharpie pens and Italian designer Armani.
He also has relationships with Germany's Volkswagen and Japan's Sony through his youth football academies.
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Beckham, who is on loan to Italy's AC Milan club until the MLS season begins in March, scored a 75.57 on the Davie Brown Index in April. The index is used by clients to determine a celebrity's ability to influence consumer awareness.
That ranks him ahead of such athletes as NASCAR driver Dale Earnhardt Jr and Chinese basketball star Yao Ming, and just behind popular golfer Tiger Woods. Forbes magazine in April 2008 estimated Beckham was the most highly compensated football player in the world at $49 million for 2007.
Delzell said he sees no reason why Beckham cannot remain a marketing presence after his retirement, just as pro basketball star Michael Jordan has done...
..."His pulling power is still very strong. He has increased revenue year on year, even last year," said Simon Oliveira, a spokesman for Beckham. "In reality, he's very much at the top of his game when it comes to those things."
Oliveira added that Pepsi was one of Beckham's smaller deals, and the focus with any new deals has been to provide Beckham with royalties or even equity so he can share in the success he brings to a company.
His star may have waned, but Beckham still gets plenty of attention and that ultimately is what sponsors care about, said Eric Wright, a vice president at Joyce Julius & Associates, a sponsorship evaluation firm in Ann Arbor, Michigan.
"The guy gets a lot of pub," Wright said of the attention Beckham gets from the media. "That's an attractive element for a brand to be able to go beyond the sports sponsorship realm and have a shot in People magazine."