Farrell was banned for one game for the incident.
“I spoke to Waney shortly after being charged for striking with the knees, and we agreed that taking an early guilty plea was the best thing to do,” Farrell said in his Wigan Today column.
“Just to be clear, I didn’t intend to hit Stefan Ratchford with my knees, but it was a clumsy thing to do.
“I shouldn’t have slid in like I did – frustration got the better of me, seeing him go under the sticks for a try. As I say, it was the wrong thing to do, I apologised to Stef afterwards and I’ll cop the ban on the chin.
“It was a bit of a poor first-half all round on Friday night. Before that, I was sinbinned for holding a player down, when Warrington broke through.
“Our defence was still getting back in place, I was trying to buy as much time as possible, and I got pinned for it.
“I was sinbinned at Leeds last year for stopping someone scoring, but on that occasion I knew I’d get sinbinned! I was in an offside position when I made a tackle.
“But on Friday, it certainly wasn’t my intention to get sinbinned – I thought I was okay, but I ran the risk and I can’t really complain. It didn’t help the side as we let in three tries in that first 20 minutes.”
Farrell will miss Wigan’s game against Wakefield on Sunday.
“We’ll be down to the bare bones for Sunday’s game and it will be hard for me to watch on, especially being fully fit but suspended,” he said.
“We had a good break over the weekend to freshen up after Easter, and I’m sure Waney will put a big emphasis on going to Wakefield with the right attitude.
“At any time, it’s a hard place to go to.”
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