New England Patriots quarterback Tom Brady has had a four-game ban restored over allegations footballs were deliberately under-inflated before an NFL play-off game last year.
Brady, 38, and the Patriots were sanctioned after a 243-page report into what became known as 'deflate-gate'.
Brady's ban was overturned in September by a federal judge, who said the NFL's ruling had "legal deficiencies".
But the NFL's subsequent appeal was upheld on Monday.
Brady is now set to miss the first four games of the 2016 season, which starts in September.
The four-time Super Bowl winner, considered one of the best ever quarterbacks, maintains neither he nor the club did anything wrong.
The Patriots won the match in question - against Indianapolis Colts in January 2015 - 45-7, and then won the Super Bowl.
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The league fined the Patriots a record $1m (£660,000) and stripped the team of two draft picks, with its report finding Brady was "generally aware" of the scheme.
NFL commissioner Roger Goodell's inquiry concluded Brady "knew about, approved of, consented to, and provided inducements and rewards" to ensure balls were deflated.
But US District Judge Richard Berman found the league's disciplinary process was "fundamentally unfair" and there were "several significant legal deficiencies" in the penalty issued by Goodell - including failing to notify Brady about the possibility of a punishment.
After his ban was lifted in September, Brady played the full season - his 16th as a professional footballer.
He said at the time: "I don't think it has been good for our sport, to a large degree, we have all lost."
Deflated balls are considered easier to throw and catch.