Boyd came out this week and said he was eager to test himself at the highest possible level before his career was over prompting Johnston to suggest that 15 Scottish Premiership goals this season has vindicated the desire of the former Rangers man.
"I'm sure there will be loads of clubs looking at Kris Boyd, the way he has played this season. He has been fantastic for us," said the Killie boss.
"And he has still got the ambition to play at the highest level. You want that. If players play with hunger, they play better.
"So I'm not disappointed that teams are showing an interest, it just shows how well he has been doing.
"We want to keep our best players. We have already said to Boydy that we want to keep him next year, but time will tell if that happens.
"I think it would take a really, really good offer to a big club for him to move because he is happy here.
"He's a real leader on the park and a big influence in the dressing room as well. I think he is actually getting better as he is getting older, with his movement. And he is still hungry to score goals. He has definitely matured as a player as well."
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