After a T-33 finish at the Players Championship in March, McIlroy followed that up by missing the cut at the Valero Texas Open. The four-time major winner was clearly in a funk, one that dated back at least to Europe's humiliating Ryder Cup defeat the previous year.
McIlroy was struggling for any kind of form heading into the Masters, but revealed it was a decision to change golf balls prior to the tournament that kickstarted his change in fortunes.
While he didn't win at Augusta, a spectacular eight-under-par 64 in his final round to finish second behind Scottie Scheffler signalled a definite cause for optimism.
Victory soon arrived at the RBC Canadian Open in June, and was followed by another big win at the PGA Tour's season-ending Tour Championship, along with a third FedEx Cup crown.
Fast forward a couple of months and McIlroy was also able to wrap up his fourth Race to Dubai title by finishing the season as European number one.
It's a turnaround in fortunes he couldn't help but reflect on with his caddie Harry Diamond as he was walking up the green on the final hole of last week's DP World Tour Championship.
"Yeah, [I am] very proud of myself. Harry and I were talking going up the last fairway. It seems like it's a long time since San Antonio, the Texas Open the week before Augusta this year when I was sort of struggling a little bit and made a couple of tweaks with my game and with my equipment.
"[I] went to a different golf ball. It seemed like just after that, my whole year turned around and got a ton the momentum at the Masters and just went from there."
McIlroy swapped out the TaylorMade TP5 for the TP5x and suddenly found he had more control.
Now he once again feels like he has more than one string to his bow.
"I think one of the things I'm really proud of is I don't feel I have to rely on one aspect of my game. I think if my driving isn't there, then my putter bails me out," he said.
"If my putter isn't there, my iron play bails me out. I feel like when you get to this level, it's like, okay, how can you make those incremental improvements to get better, and I think my goal has been to just become a more complete golfer and I feel like I'm on the journey to doing that.
"But I definitely -- I'm as complete a golfer as I feel like I've ever been, and hopefully I can continue on that path."