As United and Chelsea are reportedly ready to go head-to-head for the 20-year-old in the summer, the clubs' players have already started social media tug-of-war over the winger.
The BVB winger turned 20 on Wednesday and Rashford took to Instagram to send his greeting to his England teammate.
"Happy birthday bro!! @sanchooo10 Enjoy your day, indoors!" the United forward posted.
To which the birthday boy replied: "Thank you Rashhyy, appreciate it bro".
As United and Chelsea are reportedly ready to go head-to-head for Sancho in the summer, Abraham, a childhood friend of the Dortmund winger, was quick to warn Rashford.
"Stay away from my Jadon," Abraham responded.
United, meanwhile, are said to be leading the race for Sancho with Borussia asking no less than £120m for the 20-year-old.