Last seen finishing third in the Tattersalls Gold Cup at the Curragh in May, he has been off since May as the heatwave rendered the ground too fast.
Prior to that, Defoe recorded wins at Newmarket and Newbury this season to take his tally to seven victories in 11 career outings.
Varian said: “We are training him for the Grosser Preis von Baden at Baden-Baden on September 2, which is a mile-and-a-half Group One.
“Ground is a big thing for him and it is just the fast ground we want to avoid.
“He won the Jockey Club Stakes on good ground earlier in the year and he obviously handles soft ground very well, but fast ground is what we want to avoid.
“Absolutely we think he is still an Arc horse as he has got some of the best middle-distance form around from earlier in the season. If he does get soft ground he is very good on that.”