Shearer wrote in The Sun: "O'Neill arrived after the departure of Steve Bruce and gave the club an immediate boost with seven wins from his first 10 games to hoist them up the table.
"Then the season fizzled out and he now has a worse record this season than Bruce had when he got the push. It is just two wins from their last 23 league games.
"Just as well O'Neill is not a Geordie like Bruce or he would have been hounded out by now!
"As it is, the fans have not turned - but they are on the brink. If they don't beat Reading at home tomorrow their patience will snap. I got to know Martin well from working with him for the BBC.