The Egyptian has scored 39 goals in all competitions and while Carragher had been backing De Bruyne for the top award, Salah's seven goals in his last four games has seen him completely change his mind.
The victor will be announced at the PFA's annual awards ceremony in London on Sunday, April 22.
City's Belgian star has been largely superb all season and was at his best early in the term as the Sky Blues took a stranglehold on the Premier League title.
GettyMohamed Salah scored yet again for Liverpool on Saturday
Salah or De Bruyne are expected to pick up the gong at the prestigious end of the season awards ceremony, and whoever wins the award will succeed Chelsea's N'Golo Kante, who was crowned the victor of the 2017 edition of the prize.
De Bruyne and Silva have, literally, been central to City rise to the Premier League summit this season.
Manchester United goalkeeper David de Gea completes the shortlist.
The left-back-cum-winger has been the key man as the Cottagers have enjoyed a brilliant season in the second tier, and they look well set to gain promotion, either by finishing second or winning the play-offs.
Manchester City are in the league of their own this season - having won 27 of their 32 round of matches already played this term.More news: US, France and United Kingdom launch strikes on Syria
More news: British cabinet agrees 'need for action' in Syria
More news: Mega Millions Jackpot victor announced