Prso was forced into early retirement by a troublesome knee injury

Dado Prso says he understands why four Rangers players have pulled out of the Scotland squad to face Croatia.

Barry Ferguson, Lee McCulloch, Christian Dailly and Allan McGregor have all withdrawn from George Burley's squad for the friendly at Hampden.

"We are not machines. It's impossible to perform at your best when you're playing every three days," Prso said.

"Why continue to suffer? Why not have a rest?" Prso said, in reference to the gruelling season the players have had.

Interview: former Rangers striker Dado Prso

Rangers are involved in three competitions, having already won the CIS Insurance Cup, and have already clocked up in the region of 50 games, with a host of fixtures still to play.

The Ibrox club face Sporting Lisbon in the first leg of their Uefa Cup quarter final on 3 April followed by a Scottish Cup semi-final replay with Partick Thistle 10 days later.

It's impossible to perform at your best when you're playing a game every three days Former Rangers and Croatia striker Dado Prso

The Scottish Premier League leaders have 10 remaining league games as they look to wrest the title from rivals Celtic for the first time since 2005.

And former Rangers and Croatia striker Prso knows from his own experience the heavy toll too much football can take on a footballer's body.

He was forced into early retirement at the end of last season after conceding defeat to a long-term knee injury.

"I spoke to Barry Ferguson and he says Rangers have already had to play 50 games. That is really a massive ask for any player," Prso said.

"I can understand why some players need to have a rest after a run like this. There are a lot of games."

Prso insisted that the Ibrox players cannot be expected to take any chances with Saturday's Old Firm derby looming.

"I know everyone always wants to see them at their best but, even if you have a rest and are very professional, it's very hard," he said.

Forward Kris Boyd is the only Rangers player left in Burley's squad for the manager's first match in charge.

And Prso has backed Boyd as the man most capable of getting the crucial goals that would help Rangers stretch their lead over their Glasgow rivals at the top of the SPL to six, with a game in hand.

MY SPORT: DEBATE Do you agree with Dado Prso about the Scotland call-offs?

Boyd has been heavily criticised for his perceived lack of work-rate despite a prolific scoring record.

"I like Boyd," Prso said of his old strike partner.

"He is the man for Rangers, he can always score goals and that's the most important thing for a striker."

"He has to improve other parts of his game, yes, but I think he can always score.

"It's up to Walter Smith to decide who should start on Saturday, I'm not the coach.

"But Boyd, even when he is not running all about the pitch, is always there in the box and you can count on him.

"It's nice for the team to know they have a man like him."