For Woods, the doubt is over a sore left elbow that has sidelined him since a poor showing at the US Open in mid June. For McIlroy the uncertainty is to do with the poor form that has afflicted him since changing his clubs and balls.
Woods had a great start to the year, winning four tournaments in his first six stroke-play events, finishing in fourth place at the 2013 Masters and regaining the world number one spot from McIlroy.
McIlroy has been similarly quiet in the buildup to The Open. He also struggled at Merion, where he tied for 41st after closing rounds of 75 and 76, before missing the cut at The Irish Open at the end of June.