Masar won last year’s Derby but he has not been seen since that race on June 2, with connections deciding to give him a longer break.
Appleby has been pleased with his stable star after a recent gallop on Wednesday, while he also completed a run around Newmarket on Saturday.
Masar is being lined up for either the Princes of Wales’s Stakes or the Hardwicke but Appleby is in no rush to decide just yet.
He told Sky Sports: ‘I was delighted with the way he came out of Saturday.
He did a routine bit of work, but rain stopped play in allowing us to get over the road on to the Limekilns.
I couldn’t have been happier with his work.
‘In regards to whether he runs in the Prince of Wales’s or Hardwicke, a decision will be made in the next 48 hours.
I don’t want to put it further back, but there plenty of calculations that need to be made, especially with the way the ground is with the rain.
‘You would be hoping for decent ground, but the forecast has changed over the last couple of days and that has to be taken into consideration.
I will speak to Sheikh Mohammed and we will make what we think is the right call for the horse for his start at Ascot.’