It’s wrong because there is no subject. And ‘debut’ is a noun or a verb, not an adjective. So you’ve made up a noun phrase, ‘debut game’ which is understandable but not natural.
Examples:
He did well in his debut. He went 2 for 4.
I’ve bought tickets for his major league debut.
He debuts with the Yankees next week. I can’t wait.
In general, ‘debut’ as either noun or verb isn’t that common a word. It’s fairly highbrow from French. As a lower level speaker you would risk not being understood. More natural would be to use a standard adjective: ‘I can’t wait for his first game.’ That’s something anyone could say.