The 34-year-old, on his comeback after a 12-month injury lay-off during which he had ankle surgery, told a news conference: "I've gone from ready to retire to couldn't be happier with the way I've bowled."
McGrath, who completed figures of five for 37 on the second day to help bowl Sri Lanka out for 97 and leave them battling to avoid defeat, said he had had a conversation with Test team mate Justin Langer last week while playing in Darwin for Northern Territory against Sri Lanka.
"It was a bit of a roller-coaster ride," McGrath said.
| |||||||||||
"I woke up the next morning and the ankle felt great. I ran in and hit the crease hard and it was like a total reversal overnight. Justin thinks you've got to hit rock bottom before you can really turn things around."
Australia have set the tourists a daunting 312 to win on a seaming wicket, while McGrath has moved to fourth on the all-time list of Test wicket-takers with 435 in 96 matches, surpassing Richard Hadlee of New Zealand and India's Kapil Dev.
"You look at the guys, Sir Richard Hadlee and Kapil Dev, they were both in front of me but not too many wickets away," McGrath added.
"There were a few stages there that I wondered if I would ever catch them. So to get those five wickets and go past two legends of the game is a pretty big buzz."
"And to get my confidence back in this match, so I couldn't ask for much more."
"It's been a good few years since I have really been that happy with bowling."
"The ankle was worrying me at the time and I thought: 'Is it going to get any better?' If not, it is hard to run in and bowl that way."
