McKenzie is currently at the Senior Bowl in Mobile, Ala., and is expected to make his decision this week.
McKenzie told Comcast SportsNet Bay Area that he has a meeting planned with Allen on Tuesday night, but he hasn't made an offer and it isn't guaranteed that the coach will receive the job.
"There's no negotiations (right now)," McKenzie said, adding that whether or not other candidates still will be considered "depends on (Allen's) interview."
Allen has "a lot of stuff he needs to answer," McKenzie said. "Nah, it's not a lock, (regardless) of other people's reports."
The other candidates interviewed haven't been asked back for second meetings and at this point don't believe they're still a part of the process, sources told La Canfora.
If Allen does land the job, he would be the first defensive-minded Raiders coach since John Madden was hired before the 1969 season. Late owner Al Davis exclusively hired offensive coaches after Madden, including Jackson.
The Associated Press contributed to this report.