Seven-year-old Reggie, accompanied by his dad, held up a sign during the Blues 3-0 win over West Bromwich Albion on Monday night, which read: "Azpilicueta (Dave).
"I broke my thumb yesterday playing football. I can't play for 4 weeks.
"Could you cheer me up by giving me your shirt? PS. Can any of you sign my cast? Thank you."
The photo went viral on social media, and Azpilicueta eventually responded.
The 28-year-old replied on Twitter: "Hi Reggie, tell your family to contact me right here and I'll be happy to send you a signed shirt. Take Care!"
Hi Reggie, tell your family to contact me right here and I'll be happy to send you a signed shirt Take care! #BlueFamilypic.twitter.com/tYZl5p5ljw
— César Azpilicueta (@CesarAzpi) February 13, 2018
@CesarAzpi Reggie says Thankyou #bluefamilypic.twitter.com/q8MBREqfIM
— Maria stewart (@Mariast09893465) February 13, 2018