The forward is enjoying a purple patch, having now scored eight goals in the five games since moving back to the club from SuperSport United in January.
However, Barker has called for consistency if Rayners wants to attract national team coach Hugo Broos’ attention.
"I think if maybe he had come a bit earlier and maybe in a month or two's time, if he continues with his form, maybe he gets a shout," said Barker.
"If you look at the strikers that have been selected, they've also shown good form of late so... [We are] a little bit disappointed for him, he's a little bit disappointed [too] but he just has to continue doing what he's doing and scoring goals."
Broos will trim his 35-man preliminary squad to 23 at the SABC headquarters in Auckland Park tomorrow, ahead of facing Liberia in back-to-back Africa Cup of Nations qualifiers this month.
Barker feels Rayners can be an alternative in future matches.
"I think he brings a different element as a striker up front, with his pace and ability to stretch defences and get in behind, his ability on set-plays and set-pieces is also of a high level, so hopefully if he continues this form he will hopefully get a shout," he added.
Prior to his reunion with Barker, the forward looked out of place at SuperSport with only five assists and no goals from the 14 games he featured in.
But Stellies know just how to put him to good use.
"Ja, look, I think Iqraam is a very underrated goal scorer. He's shown for us, when he helped us get promotion in our first season, he's a goal scorer and he's very comfortable in front of goal," said Barker.
"I think we're just maybe playing him in the position that we believe gets him the most opportunities because we know when he gets those opportunities, he'll take them.
"Currently he's almost two goals per game for us in just the short stint that he's been back – eight goals and two assists, and if you add the goals he scored and assists at SuperSport, he's probably one of the leading players in goal involvements for the season."