Japanese Matsuyama had picked up three straight birdies to jump into second place at six-under after 14 holes, with Australian Day in third place at five-under after 10 holes.
Players with one hole left ran to their last tee to fire off a shot before the horn sounded to suspend play for the day so they would be allowed to finish the hole and their round, and not have to return early on Saturday to complete it.
Third-ranked Matsuyama, trying to become the first Japanese man to win a major title, and 25th-ranked American Kisner, who won his second U.S. tour title in May at Colonial, still shared the second-round lead on eight-under par 134. Jordan Spieth all but ruled himself out after failing to take advantage over the last seven holes after the rain.
It was a welcome return to form for Jason Day who has struggled this season and the 2015 victor sits in third, two shots off the lead.
That was still good enough to remain in contention, a stroke behind Kisner, who dropped three shots in the final three holes.
Peter Uihlein (OSU): Uihlein shot his second consecutive 3-over 74 and is tied for 78th at 6-over 148, one shot short of making the projected cut of 5-over 147.
Graham DeLaet led a group of five players at 2 under by completing a birdie-eagle-eagle-birdie stretch on the back nine. Fowler was 5 under for the tournament heading into the 16th, but he finished bogey, double-bogey, bogey to fall back to 1 under.
"This is my first experience leading a major, or tied for the lead after 36 holes. I was hitting fairways but I wasn't getting the crisp contact that I was hoping for".
After a fairly creditable one-over 72 overnight, it took Lahiri 12 holes to find his first birdie in the second round and he added a second on 18th, which he played as ninth and birdied on Thursday, too.
"I was grateful for the rain delay because I was getting exhausted".
Fox's 66 was the low round of the tournament till that point, and comprised four birdies on the front nine and a further two, plus a lone bogey on the par-four 11th, on the inward nine.
"I'd love to know what he thought he could really do with that second shot". I probably didn't quite hit it as well off the tee as I did yesterday, and wasn't putting myself in positions where I could go at a lot of pins.
"Luckily it got out of the bunker and on to the other side".
"I've got to make up ground".