LEMONT, Ill. — Feeling as though he had nothing to lose, Justin Rose put himself in position for a big gain with his best round of the year Thursday in the BMW championship.

Rose made birdie on half of his holes at Cog Hill, a tough course that played even longer in chilly conditions, giving him an 8-under 63 and a two-shot lead over Webb Simpson and Mark Wilson.

“Didn’t expect that going out there today,” Rose said. “I looked to the weather, looked at the temperature, and I thought today was going to be a day to hang in there. Little did I know I was about to play so well — certainly my best round of the year by a long, long way.”