A former member of the Ciaron Maher team, Sir Davy will be having his first start for McCarthy in the VRC Member Lilly Liu Sprint (1200m) at Flemington on Saturday.
McCarthy said Saturday's contest was the ideal hit-out for the Forbes Cup (1600m) on August 4.
Sir Davy won seven of his 25 starts under the care of Maher and former co-trainer trainer David EustaceHe was successful at Moonee Valley in March before unplaced runs at Bendigo and Warrnambool to end his campaign with the country's leading trainer.
McCarthy revealed he purchased Sir Davy online for $45,000.
"He's a lightly raced horse that has been pretty successful through his career and I thought there might be a little bit more left in the tank," McCarthy said.
"Going forward he's VOBIS Gold eligible and there's all those VOBIS Gold races that are really suitable for the horse with his sort of rating.
"With a new group of owners, we thought they might be able to have a bit of fun."
After spelling at Maher's Ballarat property, Sir Davy was put straight into work and won a Wangaratta trial in preparation for Saturday's contest.
McCarthy said Saturday's trip was likely to be too short for Sir Davy, although the gelding has had limited luck in his two previous tries at the trip.
"He was pretty impressive in the trial and came through it pretty well," McCarthy said.
"His best form looks like it's over further, but it will be nice to kick him off and hopefully see him run a nice race.
"His only run over 1200 metres at Flemington was in the Creswick (finishing ninth) and he was desperately unlucky that day.
"That was a fair while ago, but his only two runs at 1200 metres have been good."
Daniel Stackhouse takes the ride with Sir Davy drawn out in gate 15 in the 16-horse field.
