The Watford legend was a tough cookie in his heyday - just ask the glut of Premier League defenders who came up against him.
And it was much the same for his Watford teammates in training - a place closed off to the regular supporter.
It was there that a former teammate left a lasting impression on the Birmingham native that others did not see.
Deeney lined-up with differing generations of players from former Arsenal goalkeeper Manuel Almunia to exciting Brazilian forward Joao Pedro who is now making waves at Brighton.
You could be forgiven for thinking the striker saw as many players come and go as he did managers during his 11 year spell at Vicarage Road.
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However, one player sticks in Deeney's mind as the most underrated during his time at the club and even took him by surprise one evening on the proverbial rainy Tuesday night at Stoke.
"Gerard Deulofeu instantly comes to mind," Deeney told talkSPORT when discussing who impressed him most in training.
"Injuries blighted him, but wow. Wow, so quick. Knew he was going to come in, playing on the left, knew he was going to come in on his right foot, but can't stop him.
"Able to hit that cross, knuckleball whip thing that he did," Deeney recalled. "He's just so good, and also so disciplined and dedicated.
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"When he first came in, I thought, 'Oh, we've got a bit of a show pony here,' and it's probably not what we needed.
"And then he came in, and his first game was literally Stoke away on a Tuesday night, and it was raining, it was miserable, and we grinded out a 0-0 draw.
"He was excellent. He did all of the graft, and then he had a little bit of spark as well."
Deeney also reserved a special mention for former teammate Maxi Pereira who left him equally impressed.
"The other one would be Maxi Pereyra as well, obviously Argentinian international, but I didn't know too much about him before he came," said Deeney.
"But when he came, I was like, 'Oh, that's why you played for Juventus.' You could put him anywhere, and he didn't care.
"He was like, 'Just give me the ball, and just watch what I do.' And yeah, those boys were a different level."
Spain international Deulofeu has been somewhat of a journeyman throughout his career which included a spell at Everton before later joining Deeney at Watford.
After starting his career at Barcelona, the exciting winger has been unable to find stability having been loaned out six times since making his professional debut in 2011.
Deulofeu left Watford in 2021 after three years at the club boasting a record of 17 goals in 70 games.
Among them, was a superb display in a 5-1 win over Cardiff in 2019, where he became the first Watford player to register a Premier League hat-trick.
The 30-year-old now calls Italy home after sealing a switch to Serie A outfit Udinese three years ago.
He missed almost the entire 2023/24 campaign after picking up a serious knee injury sustained in a fixture against Sampdoria in January 2023 and is yet to feature this season.
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