FALMOUTH – For someone who has never played in the Maine Amateur Golf Championship before, James Frost Jr. of Calais is giving the appearance of being a veteran.

The 19-year-old Frost won two matches Thursday at Falmouth Country Club to become one of four players to advance to today’s semifinal round. Along with Frost are defending champion Mark Plummer of Manchester, Scott Dewitt of Biddeford, and Todd Kirn of Sanford.

Frost will face Kirn starting at 8 a.m., and Plummer takes on Dewitt 15 minutes later. The two winners are scheduled to square off at noon for the title in this 83rd edition of the tournament.

“I did better than I expected,” said Frost. “I was just looking to make it into the quarterfinals.”

He’s ready for more, though.

“I feel confident, I just have to drop a few more putts,” said Frost.

Frost dropped enough putts to win 2 and 1 over Sam Marzenell, one of four Biddeford-Saco Country Club regulars to make the top 16, in the morning and 3 and 1 over Ben Daughan of York in the afternoon. Daughan topped Alan Bouchard of Falmouth 3 and 2 in the morning.

Plummer was also a 3 and 1 winner in the afternoon, over Jay Livingston of Hermon, after downing Ricky Jones of Rockland 2 and 1 in the morning. Livingston cruised past Joe Manganaro of Gorham 6 and 5 Thursday morning.

Livingston thought his morning victory might be a preview of things to come.

“I was playing so well this morning, I thought it was my day,” said Livingston. It didn’t carry over into the afternoon round.

“[Plummer] made some mistakes. I just didn’t capitalize,” said Livingston.

Dewitt downed Windham’s Shawn Warren, co-medalist in the two days of stroke play, 3 and 2 Thursday afternoon. He downed Joe Alvarez of Veazie by the same score in the morning. Warren topped Les Fleisher of Cape Elizabeth 2 and 1 in the morning.

Kirn turned back Mike Nowak of Augusta 2-up in the afternoon and edged co-medalist Tom Bean of Kennebunk 1-up in the morning. Nowak stopped Keith Patterson II of Saco 4 and 2 in the morning.

The wind was blowing harder Thursday than either of the first two days, and Frost thinks that played to one of his strengths.

“For a person to play well today, they had to control the trajectory of their shots,” said Frost. “I thought I did a good job of that today.”

It came into play on the first hole against Daughan.

“I made a mental mistake in the morning,” said Frost. “I hit a high wedge in there this morning [and couldn’t control it]. I hit a low shot in there this afternoon to 2 feet. It was a smarter shot.”

Frost birdied the hole to take the lead and never trailed. Daughan did catch Frost with a little bit of luck on 13, but Frost won the next two.

“I thought the turning point was when he missed the putt on 14,” said Frost.

Both cleared the pond on the par 5 with their third shots, but Daughan was in the back collar with a downhill putt. He rolled it 7 feet past and his comebacker for par rimmed out, making a near 180-degree turn. Frost had already two-putted from 12 feet for par.

Daughan then his tee shot on 15 out of bounds and eventually conceded the hole to Frost.

They halved the 16th, but another tee shot out of bounds on 17 just about finished Daughan. He played on, but Frost, teeing off first, had hit 1-iron off the tee and was just off the left edge of the fairway.

“I was not going to hit 1-iron out of bounds,” said Frost. “I hit shots that I was confident I would hit straight.”

When Frost’s birdie putt from the left collar on the par-5 just missed going in and stopped 2 feet from the cup, Daughan conceded the hole and the match.

“I got some lucky breaks out there,” said Frost.

Frost just finished his freshman year at Campbell University, an NCAA Division I school near Raleigh, N.C. He didn’t make the top five on his team, so he played only in home matches. He’s seeing improvement, though.

“I have a much better swing now. I’m a lot more confident,” said Frost, who added that he’s transferring to get into Mississippi State University’s golf management program.

Livingston was disappointed in his showing against Plummer.

“Three-putts killed me,” he said. “The one on 12 really hurt. It was 10 feet downhill, and I hit it 4 feet past.”

Plummer agreed that hole was key.

“Instead of winning the hole, he loses the hole,” said Plummer, who has won this event 12 times.

“I just couldn’t seem to get the speed right on the first putts,” said Livingston.