kaskati

1. (+ za + instr.) to lag behind; to trail
   Naša privreda i dalje kaska za Evropom. — Our economy is still lagging behind Europe.
   Plate stalno kaskaju za cenama. — Wages keep lagging behind prices.
2. (of a horse) to trot
   Konj je lagano kaskao po livadi. — The horse was trotting slowly across the meadow.
3. (of a person) to jog along; to scurry
   Mali je kaskao za ocem do prodavnice. — The little boy trotted after his father to the shop.

In the sense "to lag behind" it takes za + instrumental: kaskati za nekim.