The 'Gers duo and their Croatian teammates face Turkey in Istanbul tonight in the first leg of their final play-off to reach next summer's tournament before the return bout in Zagreb on Tuesday.
McCulloch and the rest of the Rangers squad hope that they do well enough to reach the competition although there was a slight sense of jealousy from the Scotsman.
"These are huge games for both Nikica and Sasa. Everyone in the dressing room wished them well after our game against Dundee United," he said.
"It was great to get the win that day and Sasa and Nikica played their part as always.
"But for them the focus switched to the play-off games immediately after the final whistle.
"And you can understand why. I know from talking to the lads how important the games are.
"I just wish Scotland were involved. These are the games you want to play in."