Coutinho was poised to move to the Nou Camp during the summer transfer window after the Catalans identified him as the long-term replacement for 33-year-old Andres Iniesta.
Barcelona made a number of offers to complete his signing, but they were forced to abandon the pursuit on deadline day after Liverpool asked them to pay €200m (£179m, $234.8m).
Several reports in recent days have claimed that Ernesto Valverde's side are planning to make a new move to sign the Liverpool playmaker during the upcoming January transfer window.
But Sport claims Barcelona are now keeping a close eye on Alli's situation as they know that signing the Liverpool star won't be easy.
Alli has established himself as a key player for Tottenham in recent seasons, playing as a forward behind Harry Kane.
However, Sport says that Barcelona believe that he could adapt to a deeper role as the former MK Dons star played in the middle of the park during his early days at White Hart Lane.
Furthermore, reports suggest that the versatile Tottenham star would be more affordable than Coutinho as Spurs could let him go for around €150m – while Liverpool want €200m to part ways with the Brazilian ace.
The Spanish publication also points out that Alli is current weighing up his long-term future at Tottenham as Real Madrid are also keeping an eye to the situation.
The England international is currently in the process of changing agents and only earns around £50,000-a-week at Mauricio Pochettino's side.
The Telegraph reported last week that Tottenham are ready to offer him around £80,000-a-week to convince him to commit his long-term future to Spurs, but the player knows that other European clubs could increase that figure considerably.
In this sense, Sport says that super-agents Jorge Mendes and Mino Raiola have bothpromised Alli to help him make a move to one of the European giants if he hires their services, with Real Madrid, Barça and Manchester United the chosen destinations.