He received a two-game penalty notice after four incidents of illegal use of his knees in last week’s Ladbrokes Challenge Cup sixth round win at former club Widnes Vikings.
It is the first time the ex-Huddersfield Giants player has ever been banned, which is an impressive record for a front-row who turns 27 next month.
However, Mullally – who misses tomorrow’s Magic Weekend game against Castleford Tigers and next Saturday’s trip to Catalans Dragons – revealed he was utterly unaware he had done anything wrong.
“To be honest, I didn’t even realise I was raising my knees,” said the Ireland international.
“It wasn’t until Mac (coach Brian McDermott) told me that I’d been charged that I went to watch the clips and realised what I’d done.
“The one from the drop-out I can’t even really explain; it was a bit of a weird jump and spin in the air.
“I don’t even know what I’ve done there. It was all a bit mad.
“But the others were more down to my running style. I’ve always been like that. With my long legs, the way I do run it’s just the way my knees come up when I bump people off. I don’t intend to raise them. It did get me thinking about what if this happens all the time now and I get charged every week... I won’t be able to play again!
“It is all a bit odd but I am conscious of it now and will look to make sure I don’t get caught out again.”
Mullally, who has sat out just three games this season, added: “It is the first time I’ve ever been banned in my career. About four or five years ago they questioned a tackle I made on Ade Gardner.
“But it got thrown out as it was deemed I did have my arm wrapped around him so it wasn’t a shoulder charge.
“So it is unusual for me to be in trouble but I’ll just make sure I train hard and am ready and fit for the Challenge Cup game against Leigh Centurions.”
Mullally, a Grand Final winner last term, said: “I had a bit of a slow start to the season just after last year being such a good one for me.
“But over the last four games I do feel like I’ve been building each week so it is a shame to be missing out now. The most disappointing thing is I’m missing Magic Weekend – I do like playing there – but I’ll look to that Leigh quarter-final now.
“People will say they’re a Championship side so it’s a good draw but we can’t under-estimate them. They’ve plenty of Super League players in that team and we have to treat them like a top Super League side. If we don’t we’ll only have ourselves to blame if we get undone.”
Leeds welcome back Ryan Hall and Brett Delaney to their 19-man squad to face the Tigers. Hall has recovered from a dislocated shoulder incurred against Widnes last week while Delaney has not featured since the win at Hull KR three weeks ago. Cameron Smith comes in for Josh Walters. Castleford make just one change to last week’s 19-man squad with Gadwin Springer making way for Kieran Gill.
Castleford Tigers: from Cook, Ellis, Foster, Gill, Hitchcox, Holmes, Massey, McMeeken, McShane, Millington, Milner, Minikin, Moors, Sene-Lefao, Shenton, Trueman, Wardle, Watts, Webster.
Leeds Rhinos: from Golding, Briscoe, Watkins, Hall, Moon, Myler, Cuthbertson, Parcell, Jones-Buchanan, Ablett, Ward, Dwyer, Delaney, Ferres, Peteru, Handley, Walker, Smith, Oledzki.
Referee: Chris Kendall.
Kick-off: Tomorrow, 7pm.