Forrest, 27, started in four World Cup qualifiers last year, though did not play a part in Scotland's latest fixtures against Belgium and Albania.
McLeish did not field wingers in those games, however, as he favoured wing-backs for width. Forrest has returned to the latest squad for matches against Israel and Portugal.
Forrest remarked: "He spoke to me after the Albania game and just said it wasn't to be for those two games but he said I was still in his plans.
"Every time you go away it's different formations and not always the same team so I just need to keep working hard, not look too much into it and be ready for the next two games coming up.
"Obviously I was disappointed. If you ask any player, if they don't play, they'll say that. At the same time, I was glad we got the good win against Albania."