McIlroy admitted he’ll be leaving with deep concerns, particularly after a driver change didn’t go according to plan at all. “Of course it concerns me. You don't want to shoot high scores like the one I did today,” said a visibly frustrated McIlroy. “I felt like I came here obviously with a new driver thinking that that was going to be good and solve some of the problems off the tee, but it didn’t. “Obviously going to Oakmont next week, what you need to do more than anything else there is hit fairways. I’m still searching for the sort of missing piece off the tee. Obviously for me, when I get that part of the game clicking, then everything falls into place for me. Right now that isn't. Yeah, that's a concern going into next week.” Needing a second-round revival after a sluggish opener at TPC Toronto, McIlroy instead plumbed the depths with an utterly woeful 8-over 78, low-lighted by a quadruple bogey eight. Somehow, it could have been worse, a couple of late birdies saving him from finishing double digits over par. To blame it all on the bedding-in period for his new TaylorMade driver would be to ignore all the other parts of his game which coughed and spluttered. He left the course on 9-over with just three others in the 153-strong field below him. With the notoriously challenging Oakmont hosting next week’s US Open, there’s a laundry list of work-ons. “I think there's still learnings that you have to take from a day like today. Look, even though the last two days didn't go the way I wanted them to, there's still things that I can take from it, and there's still things that I can learn,” he insisted. “I'm going to have to do a lot of practice and a lot of work over the weekend at home and try to at least have a better idea of where my game is going into next week." How disorienting this must all feel, mere weeks removed from his drought-breaking, career grand slam-clinching victory at Augusta in April. In truth, it looks as though McIlroy hasn’t yet figured out what golf will look like now that he achieved his holy grail. At the PGA Championship last month, hosted at a Quail Hollow course which he has made his own, he was also fitful and frustrated. At least there he made the cut. It was clear his trip north would be a short one after the disaster came early Friday afternoon. A wild second shot out of the right rough on the 5th hole ended up with a lost ball and from there little improved as he carded an ugly quadruple eight. Another bogey at the 8th left him on 6-over with the cutline disappearing over the horizon. “I didn't hit enough fairways. I felt like I drove the ball better yesterday than I did today. I think, once I made that big number on the front nine, I was always behind the 8 ball a little bit. After nine holes, I sort of resigned myself to the fact that I'd be flying home to Florida tonight,” McIlroy said. It got worse, another wild drive on 10 the spark for another bogey and then a wet tee shot on the short 11th resulting in a double. Even the late brace of birdies was offset by one more bogey in between on the 17th. Look at the strokes gained data and there were only flashing red lights for the Holywood man. Most worryingly, he was 148th of 153 off the tee. After the driver he used to win at Augusta was deemed non-conforming in a pre-PGA check at Quail Hollow, McIlroy has been testing out a new big stick. So far it’s a bit of trial and a lot of error. “So I went back to a 44-inch driver this week to try to get something that was a little more in control and could try to get something a bit more in play. But if I'm going to miss fairways, I'd rather have the ball speed and miss the fairway than not,” he explained. “I was saying to Harry going down the last this is the second time this year I've tried the new version, and it hasn't quite worked out for me. So I'd say I'll be testing quite a few drivers over the weekend.” The Irish challenge will instead be carried by Shane Lowry who followed Thursday’s stellar 64 with a steadier two-under 68 to put himself in a halfway clubhouse tie for sixth, four shots back of leader Cameron Champ.