The teenager made a big impact in Serie A after scoring twice as Roma beat Genoa 2-0 a month later.
He was also part of the first team and made 20 appearances in all competitions, while helping Roma win the Europa League.
Afena-Gyan secured a transfer from Roma to newly promoted Cremonese last summer but still has fond memories of Mourinho’s time.
“Mourinho is my second father. He made me who I am today,” the 19-year-old told La Gazzeta Dello Sport, as quoted by 3Sports.
Meanwhile, Afena-Gyan was the hero as Cremonese beat Napoli in the Coppa Italia.
Cremonese qualified for the quarter-finals of the cup competition after beating Napoli on penalties on Tuesday evening.
The visitors took an early lead, as Charles Pickel finished well in the 18th minute after being set up by David Okereke.
However, quick goals from Juan Jesus and Giovanni Simeone saw Napoli turn the game around and lead 2-1 at the break.
Afena-Gyan replaced Okereke in the 65th minute and got the late equalizer to send the game into extra time.
The 19-year-old striker then scored the winning penalty as Cremonese ran out 5-4 winners in a shootout against leaders Setie A.
“Great team effort tonight. Congratulations to @USCremonese for qualifying to the next stage of the #CoppaItalia. If we believe, we can achieve it,” he later wrote on Twitter.