Impressing winning Ryder Cup captain Paul McGinley as he heaped praise on the Scot in his commentary for Sky Sports Golf, Forrest produced one of the best efforts of his professional career as he covered the opening 16 holes in six-under-par at Mount Juliet.
With leader Herbert in his sights, the 28-year-old Haddington-based player was unlucky to see his approach at the par-5 17th trickle off the green when it seemed he’d set up the chance of a two-putt birdie.
Having to settle for a par there virtually ended his hopes of finishing ahead of Herbert, but Forrest still headed to the final tee with a great chance of securing one of three spots up for grabs in the 149th Open at Royal St George’s.
It would have been job done if he’d finished with a par-4, but, after finding tree trouble with his tee shot, a double-bogey went down there for the second time in 24 hours.
A closing 68 for a 14-under total left Forrest in a tie for fourth alongside compatriot Richie Ramsay who picked up three birdies in the last five holes as he signed off with the same score.
The effort equalled Forrest’s best finish on the European Tour and he’ll now go into this week’s abrdn Scottish Open close to home at The Renaissance Club with a spring in his step, but this one has left a bit of a sting.
“Obviously pretty devastated with the finish,” he said. “I got a little bit unlucky off the tee, got under the tree, didn’t have a draw or anything. Had to swipe at it and missed it, and then knocked the next one out and made a pretty good 6 from there.
“It’s been a while since I’ve been right up there in an event and to be in that position was great, but a little disappointed.”
The former Scottish Amateur champion had grinded really well in the third round to get into red figures after 17 holes before ending his day on a low note. Despite a change of tactics, it happened again.
“It's not the easiest tee shot in the world,” he said. “The wind is in off the left and I tried to just hit my draw with a 3-wood. Hit 3-iron the last three days and wanted to get a little bit further up today, especially with that back pin.
“I just pushed it a little bit. Wasn't a terrible shot but being that bit further up meant I reached those little trees. Another day it might have kicked left and I'd have a shot at the green but not today.”
Herbert, 25, overcame tree trouble three holes in a row on the front nine to close with a 68 for a 19-under total, winning by three shots from Swede Rikard Karlberg and American Johannes Veerman as they all secured Open spots.
“You're not going to get my hands off this one for a little while,” said Herbert after becoming just the third Australian to get his hands on the trophy.