Keane's elevation from the Under-19s for the first time represents real progress for the youngster, who was top scorer at Academy level last season. After shining in a 4-2 win at Carrow Road on 27 September, the teenager notched his fourth goal of the campaign in the last second-string outing against Everton.
"It's a massive step for Will," Joyce explained to ManUtd.com. "It's a great little taster for him and an opportunity for him to go and work with those players at that level and the staff at that level as well.
"Ever since the Norwich game really, he's carried on his good form away with England and hopefully he'll do well with the Under-21s.
"I do think we have some good players here who don't get that recognition if they're not playing league football. We're pretty confident here that Will could be out there doing it in the league but there's things we want him to develop in-house before he goes out.
"There's two games for the Under-21s [the second fixture is against Belgium on Monday] and it'll be good for the boy."