Mamadou Sakho had previously worn the number 17 shirt since arriving at Anfield in 2013.
New number: Mamadou Sakho
Sakho has worn number 17 ever since arriving at the club from Paris Saint-Germain in 2013, and the squad number change perhaps signals just how much he is valued by German manager Jurgen Klopp.
The French international defender has had a difficult summer after being suspended by UEFA for 30 days for taking what was described as a 'fat burner', detected after Liverpool's Europa League clash against Manchester United.
Suspended Sakho was cleared of any wrongdoing
Sakho was later cleared of wrong doing after UEFA's control, ethics and disciplinary body dropped their case against him.
However, the initial suspension forced the French international defender to miss Liverpool's Premier League run-in, resulting in him missing their Europa League final clash against Sevilla, as well as more poignantly ruling him out of contention for a spot in Didier Deschamps' French national team.
This was a bitter pill to swallow for Sakho as his country were the hosts of Euro 2016, and up to that point the Liverpool defender was a regular starter for his country.
France made it all the way to the final without Sakho
But despite Sakho's absence, Les Bleus made it all the way to the final, only to be defeated by Portugal.
Nevertheless, Sakho is expected to bounce back next season and he will do so with the club's full backing, and it appears he may be set for a crucial role in Klopp's first full season in charge, despite competition from Dejan Lovren and new signing Joel Matip.
The number 3 shirt, in traditional opinion, usually signifies a more established, regular name on the team sheet. And their can be doubting that after his improved form under the former Dortmund boss last season this theory certainly will apply to Sakho.
Mamadou Sakho celebrates with manager Juergen Klopp after scoring for Liverpool last season
Some Liverpool fans will be less than pleased at the number switch, if they have already bought a number Sakho emblazoned number 17 shirt. But, in order to appease those fans, Sakho has agreed to sign any Liverpool shirt that was bought before the number change.
Details of which can be found on the club's website.