Lennon has been under increasing pressure with the team 11 points behind Rangers.
A growing number of supporters have called on the Celtic hierarchy to make a change as the club go in search of 10 in a row.
O’Neill reckons the current champions can turn the deficit around with two games in hand.
As part of his Lennon defence, O’Neill believes the Covid controversy around Boli Bolingoli and the lack of fans has had a big impact.
“The league is not over. Not by a long shot,” he told the Herald. “Can Celtic get it back? Absolutely they can get it back. Covid issues have been huge. Boli Bolingoli talking himself off for a jaunt to Spain put Celtic in bother because those games in hand aren’t a problem until your rivals are picking up a bit of momentum and then all of a sudden there is a bit of psychology at play.”
“The pressure he is under right now is entirely unwarranted for the success that Celtic have had and the part he has played in that.
“Anyone can head onto social media and stick up a poll.
“One of the strangest sights I have seen was at Celtic Park on the opening day of the season when they raised the Championship flag to empty stadium. It was quite something. If there were 60,000 fans in there I am fairly certain that there would be a fair bit of support put in the way of Neil Lennon. And rightly so.”
O'Neill has advised his former club to take Rangers out of the equation as they look to turn their form around and focus on what they can control.
Celtic face St Johnstone, Kilmarnock, Ross County, Hamilton and Dundee United in the league before the next Old Firm clash.
“Right now they need to forget about all of that,” O’Neill said. “Stop looking at what Rangers are doing and where Rangers are. You get the head down and you focus and you make sure everyone around you focused. This is total concentration now.”