The left-sided Norwegian signed for Liverpool from Monaco during the summer months and has been a revelation for the Reds, solid and attacking down the left flank and the scorer of memorable goals - notably against Everton, Manchester United and Arsenal.
Steffen feels that his national team colleague has taken the Premiership somewhat by surprise.
"Definitely," said Steffen. "I think he's been brilliant and has been one of Liverpool's best players during the season.
"I think he's done tremendously well. I always knew he was an excellent player, he didn't play that much at Monaco but got the chance to play at Liverpool and has kept his place by playing brilliantly."
Riise has certainly showed a high level of consistency, so much so that he has featured in all Liverpool's Premiership games.
"He is, and his fitness is just phenominal in internationals and stuff and even before he became an international in the under-21s. He can run all day long and he's shown that here in the Premiership.
"He's strong, he's got decent pace, good in the air and has probably got the best left foot in the league.
He's definitely one of, certainly mine, the young players of the year here I think.
"I would say he's been the best left wing-back in the Premiership this season. He's done tremendously well and has scored some great goals for Liverpool off his left foot."
Even though they will not be in direct combat on Saturday, Steffen hopes to get the run on his mate at some stage of the game.
"I'd love to play against him! I'm probably not going to play up the righ hand side, probably up front, so if he wants a little game against me he'll have to come in there. It'll be great if he does.
"I get on great with him, we usually room together for internationals, we know each other well and speak quite often. A great player and a good friend."
Steffen Iversen has no doubts about nominating his friend and countryman John Arne Riise as one of the players of the season.