King Ottokar was last seen finishing third to Sangarius in the Hampton Court Stakes over 10 furlongs at Royal Ascot, having failed to see out the mile and a half when fourth behind Sir Dragonet in the Chester Vase.
Fellowes said: “He’s in great form -we’re just picking things up (with him again).
“We’ve got a choice of a Group Three over a mile at Goodwood, or he could go for the Sovereign Stakes at Salisbury.
“We want to drop him back to a mile – we think he’s got a lot of speed.”
The Newmarket trainer will take prevailing conditions into account.
“At Goodwood I’d be concerned if the ground came up quick,” he added.
“As for Salisbury, I’d be a little bit more relaxed how the ground was.
“We’ve got options and are really looking forward to getting him back on the track. He looks a picture.”