McIlroy missed his fourth cut of the season after rounds of 74 and 72 in the Irish Open last week, admitting a new driver was still not 100 per cent right and that he was unsure of whether he would miss fairways left or right with the club.
The 24-year-old - who won five times in 2012 with his previous clubs, including a second major title - remained at Carton House for the weekend to get in some extra practice and told reporters he would meet with Nike representatives this week to continue searching for the perfect driver and putter.
"The driver hasn't been the best club in my bag this year to be honest," McIlroy said. "It's been a bit of a struggle off the tee. I base my game around that and if I drive the ball well, I am going to do well.
"So I am going to meet with the Nike guys on Thursday and test a few more drivers and try and get something set up perfectly for me so I have confidence in that going into the rest of the season as well."
Casey also uses Nike equipment and defended the company in the wake of McIlroy's poor form and his own return to winning ways on Sunday, the 35-year-old claiming his first European Tour win since January 2011 with a superb closing 67.
"Wow. I must admit, I've not had a Nike question in a while," Casey joked. "Whatever I say could be quite delicate.
"I have the fullest confidence in Rory and I think I would agree with what I've been reading, which is that Rory is kind of a streaky player, but I have 100 per cent confidence in Rory being back in the winner's circle very, very soon.
"I talk to Rory on the range but I don't know what he's working on or what he's been struggling with equipment-wise. We have so many different specs. He's using a different golf ball to me, a different shaft, a different head. It's so many variables.
"But it really frustrates me when I read negative press about Nike and their equipment. They are a legitimate golf brand, legitimate golf company, and people don't necessarily see what I see behind the scenes with the R&D (research and development) and the personnel that are making fantastic golf products.
"It's right up there; I would put three or four other manufacturers up there in the same ballpark. It is not inferior (equipment) in any way, and this is just something that he (McIlroy) is just trying to get right. I have confidence that he will.
"Last week for me the putting clicked. I actually switched putters and put a new putter in. It's the same Nike putter, looks the same but has dots on top to line the ball up; that was the only difference."
Casey was ranked as high as third in the world in 2009 before suffering from numerous injury problems which contributed to a loss in form, meaning his win on Sunday lifted him from 169th in the world to 102nd.
The former Ryder Cup star is still troubled by a toe problem and revealed he may need surgery this winter, although the chances of another broken collarbone from snowboarding appear to be over.
"My toe is actually very sore," he said. "I've got no cartilage in the right big toe joint. At some point I'll probably have an injection in it to relieve that pain and probably at the end of the year I might have it cut open and cleaned out, which might mean some time off.
"But I'm manning up and I'm dealing with the pain! As for snowboarding, I just haven't been back. I haven't really given it up. But I believe it's now in my Nike contract!"