PALM BEACH GARDENS, Florida - Tiger Woods has not won a US PGA event in 18 months and has slid from world No 1 to fifth in the rankings, but former world No 1 Lee Westwood warns not to count him out.

"Class is permanent. Form is fickle," Westwood said on Tuesday. "I would be wise enough to know not to write him off."

England's Westwood, who surrendered the top spot to Germany's Martin Kaymer this week after dethroning Woods himself last October, is among those playing at this week's $5.7 million PGA Honda Classic.