Mourinho has suggested that he will play a weakened team at Anfield as his priority is next week's UEFA Champions League semi-final second leg tie with Atletico Madrid.
However, former Chelsea defender Johnson, who played under Mourinho, says the Portuguese boss will not unsettle the Liverpool squad and that they are focusing on themselves.
"To be honest, it isn't important. We have got to worry about ourselves and concentrate on our own job," Johnson told the Daily Mirror.
"And if we play like we did against Manchester City (in a 3-2 win on April 13), we can beat anyone.
"I don't see much of it, if I'm being honest, but I can just laugh it off because that is what they do.
"Their situation is different at the minute, as they are in-between Champions League games. We don't know what their priority will be or what Mourinho is thinking.
"You try to ignore all that."
Liverpool have their Premier League destiny in their own hands, but Johnson has urged caution and insisted nothing has been won yet.
"We are keeping professional at all times," added Johnson.
"At the minute, we haven't got anything to be excited about, have we? If we lose the next three games, everything we have done over the last couple of months will be wasted.
"There are no given three points at this stage. We are going to have to earn every single one if we want to achieve what we are close to. Beating Norwich was even more important than beating City."
Watch Liverpool v Chelsea live on Sky Sports this Sunday. Kick-off at Anfield is at 2.05pm