Scotland's assistant head coach said he is "disappointed" in the recent national players who have dropped out ahead of Scotland's summer friendlies in South America.

Many of Celtic's double-treble winning players are not amongst the names of the squad after Alex McLeish and Brendan Rodgers had talks.

Celtic have a Champions League qualifier soon after the upcoming friendlies.

A total of six players have been allowed to withdraw from the squad including Allan McGregor, Matt Ritchie, Ryan Fraser, Barry Douglas, Stuart Armstrong and John Souttar.

"It's disappointing. We want people who are desperate to play for Scotland, we don't want them thinking they want an extra holiday or a rest," said McFadden.

"It's up to the players who have been called in to step up and let's see if they're good enough.

"There are players in there (and quite rightly so) that are desperate to play for Scotland.

"It's not our strongest squad by any stretch, but these players are good enough."

Callum McGregor's outstanding season and recent remarkable Scottish Cup final goal has pushed him to the forefront of national footballing spotlight.

As McFadden once was a talisman for the national side, it is hoped that McGregor can fill that role after showing what he can do this season.

"I think he'll be a hugely important player for Scotland. He is a brilliant football player.

"At times, people maybe questioned why he was in the Celtic team, now he's a mainstay and that can only benefit us as a national side."

Scotland face Peru on May 30, as well as Mexico on June 3, both games are played away from home.