The 20-year-old centre-back joins Scottish Premiership side Callie on a year-long loan deal.

Elsdon, a former England Under-17 international who joined Boro from Sunderland at the age of 14, was a member of Boro’s UEFA Youth League team in 2015/16 and featured regularly for the club in the PL2 last season. 

Elsdon's loan departure follows that of fellow youngsters Joe Fryer and Robbie Tinkler.