Isak went on strike at Newcastle over preseason to force a move to Liverpool in the final days of the summer market.
Shearer told Betfair: "It hasn't been the start to the season that Isak would've wanted. When you consider Sweden's front three of Gyokeres, Isak and Elanga and you can't score and are on the brink of not qualifying for the World Cup.
"Obviously, the manager has paid the price and lost his job which is no surprise. Obviously with the Newcastle situation, Isak not playing or training and understandably hasn't hit the ground running at Liverpool, he was probably looking to get to full fitness at this international break, but it's gone the other way.
"It hasn't worked, he and they haven't scored and can't score which, when you look at the ability of that front three, being bottom of the group doesn't look right at all. The summer certainly hasn't helped Isak."