Swansea v Arsenal - Premier League preview
Crowley was on loan at the Tykes before he returned to the Gunners earlier this week.
Initial reports claim he struggled to settle in League One, however Arsene Wenger may have recalled him to ease the current injury crisis.
With Alex Oxlade-Chamberlain and Theo Walcott both sidelined, the young midfielder, 18, could be handed his first-team debut against Swansea tomorrow.
And Johnson has no doubt he'll be ready for it.
"I think that Dan’s had a fantastic time here, we’ve really enjoyed working with him," he said.
"He’s probably one of the best, or the best, or most talented 18-year-olds I’ve ever seen.
"Obviously I came through the ranks at Arsenal as well, so there’s players like Ashley Cole that I include in that, players that have had very good careers.
"For me, it was fantastic to work with him, really enjoyed it, really appreciative to Arsenal.
"I think he had four or five really good effective games for us that showed his quality and where he could be.
"He had a couple of injuries, he was called up by England, which stunted the starts he could have had, but I’ve got nothing but positive thoughts about him as a lad and as a player."