Speaking to talkSPORT, Groves said: "I heard about him coming through Hale End and through the age groups. He was 13 playing with the U16s... I then saw him play live for the first time with the U18s against Man United in the FA Youth Cup.
"He's got this technique that you can't really coach, where he's stop-start, stop-start, so when you're taking someone on and you think you've gone past them, but he'll stop and start, and end up scrambling the opposition's brain.
"So, he is a scary talent and he'll be well-nurtured at Arsenal because they've got a good reputation of bringing younger players through, like Bukayo Saka, Ethan Nwaneri and Myles Lewis-Skelly.
"Style-wise, he's a lot like Lionel Messi. Only because he's left-footed, the same sort of build, got the balance... I'm not saying he's going to be as good as Messi because, of course, he's one of the greatest players of all time.
"Dowman has a good background to him, the only reason he won't make the level that he can with his talent, is if he's unlucky with his injuries, or his attitude isn't right. And from all the reports I've heard, he's a very well-balanced, level-headed man off the pitch, so as long as he stays like that, then the world's his lobster."