Okay...pure speculation. I base this on my experience observing my wife after she had a serious back injury. She was prescribed oxycodone over a period of many, many months. She took it as prescribed. She didn't over-medicate herself. The stuff stays in your system especially if you're taking it regularly as prescribed. Motor skills can be affected along with cognition.
This is on the pill container- "May cause drowsiness and dizziness Alcohol may intensify this effect. Use care when operating a vehicle, vessel (boat), or machinery."
Tiger had recent back surgery. It's possible he's on a regular dosage of pain medication. The time of day would seem to be irrelevant.