Shearer wrote in The Sun: "I feared from my own personal experience that Roberto Mancini and his title-winners had missed a trick when the transfer window shut last August. When you are in a position of strength, you have to make the most of it.
"That was their big chance to bring in a couple more of the world's best players to really raise the bar. But, sadly for them, they did not take it.
"To me, it brings back memories of when I won the title with Blackburn back in 1994/5.
"We were the English champions and were linked with names like Zidane and Dugarry - and while no-one expected them to walk through the door at Ewood, it did not do us any harm.
"Yet Ray Harford took over from Kenny Dalglish and wanted to give the players who had won it the chance to do it again. Sadly it proved to be the wrong call as we didn't move forward as a team and ended up finishing seventh."