Grehan’s match with Teder provided an intriguing spectacle for the large galleries following and there was never more than one hole in it as the duo traded match play blows.
One of the key moments arrived on the par-3 11th when Grehan chipped in from below the green for an unlikely birdie and Teder, sitting safely in the heart of the green, missed his putt to halve the hole.
Grehan’s slender one hole lead was wiped out, however, on the 14th when his shot hit the slope of the green and rolled back down.
The Irishman countered on the 16th, though, and inched ahead again with a birdie after his long eagle putt grazed the hole.
As the tension mounted, Teder, making his first semi-final appearance after two previous quarter-final exits, had a chance to keep the match going on the 17th.
After his long birdie putt, the 21-year-old was left with a three-footer to halve the hole, but his effort rolled past and Grehan’s final place was confirmed.
“I'm delighted. It was a really tight, tight match there," Grehan said. "Richie (Teder), I know him very well, so I knew he would produce some good stuff, which he did. Luckily I produced some good stuff myself."
“I'm playing really well. Hitting the ball great," he added. "I enjoy all the people out there, the crowds. Hopefully a few more of them tomorrow. I really enjoyed the match today, and this is what you play for, isn't it? I'm buzzing for tomorrow.”