drop back
• fall back or get left behind.
• "the colt was struggling to stay with the pace and started to drop back"
Similar:
fall back/behind,
get left behind,
lag behind,
straggle,
linger,
dawdle,
dally,
hang back,
loiter,
bring/take up the rear,
dilly-dally,
tarry,
Opposite:
go ahead,
keep up,
