The 17-year-old wide player, younger brother of Celtic and Scotland winger James, has been impressing at the Somerset Park club with, as yet, thankfully no sign of the injury woes which have afflicted his elder sibling's career.
James will miss further massive games for club and country after going down with a hamstring injury last week against Dundee United, and Alan admits it has become something of a sore point.
"It has been frustrating for James," said the Ayr United youngster, who already has 30 first-team appearances under his belt. "I can tell he is fed up with all the injuries, he doesn't want to talk about it.
"Hopefully he will be back playing again soon. So far I have been OK with injuries but you never know what is round the corner for you.
The younger member of the Prestwick-based Forrest clan, also a winger or striker, was at Celtic himself until the age of 14. "I left because I was playing out of position, I wanted to play further forward," he said.
"They were playing me at full back and it just wasn't happening for me. I decided to leave and I guess it has worked out for me so far."
Ayr are two divisions below Kilmarnock but have a good history in this fixture, even if they lost heavily in a closed-door bounce game between the two sides in Largs as recently as this summer.
While Forrest is far too young to remember Andy Walker's famous dinked penalty that put the seal on Ayr's 3-0 Scottish Cup win over Killie in January 1999 he has, however, been told all about it by Ayr's fans and senior players.
"I am buzzing for the match at Kilmarnock," Forrest said. "It will be a different experience for me, I have never known anything like it.
"I don't read too much into talk linking me with other clubs. I just need to keep playing, get a good season under my belt and take it from there."