Maybank Championship: Illness ends Willett's challenge in Malaysia
The Sheffield golfer thought he had caught a nasty cold on the flight to Malaysia for the tournament but was diagnosed with sinusitis and put on antibiotics after the end of his third round.
And he admitted after the final round that he had been struggling for energy all week.
Willett was in a strong position heading into the third round, sitting five shots off the lead.
But rounds of two over par and four over on the last two days – both featuring a double bogey – ended his challenge and left him on -2 for the week.
The event was won by Australian Marcus Fraser on -15.
Willett will take a break before returning to action in the United States at the WGC Cadillac Championships in Doral, Florida on March 3.
He finished in a tie for 12th at the event last year.
Fellow Sheffield golfer Matt Fitzpatrick missed the cut at the Maybank Championship.
MAYBANK CHAMPIONSHIP LEADERBOARD
1 Marcus Fraser -15
T2 Miguel Tabuena, Soomin Lee -13
T4 Julien Quesne, Jorge Campillo -12
T6 Richard Bland, Pablo Larrazabal -11
8 Nathan Holman -10
T9 Peter Uihlein, Rahil Gangjee, Masahiro Kawamura -9