“Marcos plays so many games on that wing and I don’t think people can imagine how hard that job is because it’s always attacking-defending, attacking-defending,” Courtois told the Chelsea website.
“You don’t stop, you’re running a lot, and he’s playing almost every three days. He does very well for us and he’s improved very much throughout last season and this season as well.
“His quality of free-kicks is amazing and those situations in football nowadays are so important, so if you can score from that it’s very good.”
Chelsea’s shot-stopper went on to offer an insight into Alonso’s trademark free-kicks, with the Spaniard’s goal against Southampton on Saturday proving enough to claim all three points.
“I only saw it quickly on the screen, but I think the wall jumped the other way, so that’s why the ball got past on that side,” he continued.
“Obviously it’s a bit annoying for a goalkeeper if you put your wall and it jumps the other side and it leaves a gap. You see the ball very late and it’s hard to save. But from our point of view, it’s very good.”