As Sheffield United manager, Warnock needed Benitez's Liverpool to get a result at Fulham late in the 2006-07 season.
The Spaniard picked what Warnock deemed to be a weakened team and Fulham won 1-0. The Yorkshireman said he would "never forgive" Benitez, whose legal team subsequently sent him an email warning of possible legal action were he to be mentioned again.
United lost their top-flight status on the final day and have since been relegated to the third tier of English football.
"Enough water's passed under the bridge," Warnock said. "It's one of those things that disappoints you in life and you have to get on with it really, but you get disappointments in every walk of life and I've made my feelings clear over the last few years - and nothing will change that.
"I think it (the email) had his name on, I think it was his solicitor who was threatening legal action and I've got it in a scrapbook at home."
Current Leeds boss Warnock said he does not know if he will shake Benitez's hand before or after the match at Elland Road.
"I've no idea, I haven't thought about it yet, I was too worried about Ipswich (last Saturday)," he quipped.
Benitez said on Tuesday that he would shake hands with Warnock. "I'm professional so will do my job. I will behave," he said.
Warnock led QPR into the Premier League and also managed Crystal Palace in between the two jobs in Yorkshire.
He said he has no regrets about turning down the Chelsea job in the early Nineties to remain at Notts County. Ken Bates - the current Leeds chairman - offered Warnock the job in 1991, but after guiding County to the top flight following successive promotions, he decided to stay put. He was sacked two years later.
"I don't have any regrets really because your life shapes around decisions and I was a northern lad and I thought going beyond Watford was the end of the world in those days," he said.
"I went down twice, once to the ground and once to Ken's farm in Beaconsfield and I was stuck on the motorway for five hours on both occasions and it didn't seem to be me really, so there are a lot of issues. I wanted to stay loyal to a group of players who had been fantastic for me.
"If it was a different way round, why do managers say loyal, you get the sack anyway, why not go and take the opportunity? Good luck to you. I've nothing about this loyalty thing now. My advice to young managers is if you get the chance, go. You get kicked in the teeth if you stay so you can't win either way."
After going through nine managers since Roman Abramovich bought the club from Bates in 2003, and Benitez only in temporary charge until the end of the season, the Blues are seemingly the perfect example to illustrate Warnock's point.