The Croatian midfield maestro demonstrated his class in Real Madrid's come-from-behind win against Paris Saint-Germain on Wednesday night in the Champions League to book their place in the quarter-final.
Modric provided the assist for Karim Benzema to score the second in the 3-1 victory.
The Ibrox legend was assistant to Walter Smith when he was sent on a scouting mission.
However, it was Modric who caught the eye and not the intended target.
"Walter sent me over to Dinamo Zagreb to look at the right back who went to Spurs as well, Vedran Corluka.
"He phoned me after the game and said 'what do you think?' and I said 'I'll tell you gaffer, they've got a wee boy in the middle of the park, he's absolutely outrageous, see how much money we've got'.
"I think we could have got him for £3.5million but we didn't have the money."
Modric would join Tottenham Hotspur for £16.5million in 2008, with Corluka joining him a few months later.
"Aw wow," McCoist added. “We didn't have the money. He asked 'how much?' and I said three and a half million and he said we can't afford it.
"What a football player. He's been great to watch."