Speaking on Match of the Day, Shearer said: "I also understand there are two sides to every story. We have never heard anything from him or his side yet - it's all leaks and reports. There is still a chance, albeit a small chance, he could be integrated back into the team if he says, 'Sorry.'
"If he wants to do that, I don't know. It's unlikely that is the case. But if it gets past the transfer deadline day and there is still an impasse and it's a deadlock and no one is budging and he is still at Newcastle, I can't see a way back then, because it's, 'Well, I have to be here.'"
The Magpies are yet to secure a new striker after missing out on transfers for players including Liam Delap, Bryan Mbeumo and, most recently, Benjamin Sesko, who chose to join Manchester United instead. In Saturday's 0-0 stalemate away at Aston Villa in their Premier League curtain-raiser, Anthony Gordon was utilised as a makeshift centre-forward with Harvey Barnes and summer acquisition Anthony Elanga flanking him.
With Callum Wilson also departing as a free agent, Howe's choices are limited, with Will Osula representing another option. The club are pursuing Brentford striker Yoane Wissa, whilst Paris Saint-Germain forward Goncalo Ramos has also surfaced as a potential transfer target.
If Newcastle were to allow Isak to leave, it's understood they have been hoping to sign a replacement first. They may not have much time to do so, as reports from journalist Sacha Tavolieri suggest the Merseysiders told the Magpies they will move onto alternative targets if a deal is not agreed by next week.
Howe recently said he may attempt to speak with Isak once more, but confessed he is uncertain whether he can persuade the Swede to reconsider his stance. Even if he manages to do so, Shearer believes it could prove challenging for Isak to regain favour with supporters and his team-mates.
The Geordie legend added: "Alex is not going about it the right way at all. You have to feel sorry for the players and the manager. The players today are busting a gut for the football club, for the thousands of fans who have travelled all that way to Villa Park, they are giving it their all.
"Yet, they are looking at another player, wherever he is, refusing to play despite having a three-year contract of over £100,000 per-week, whereas the fans are paying £60 or £70 for a ticket, £30 for petrol or a train ticket to get there and back.
"You can imagine the anger they are feeling that someone is taking the liberty of saying, 'I'm refusing to play.' You just cannot do that when you've got a three-year contract."