Translation of "Workhorse" in Spanish

Somewhere in La Mancha, in a place whose name I cannot recall, there lived not long ago a nobleman. To his name he had a lance in its sheath, an old leather buckler, a scrawny workhorse and a greyhound that scurried about.

En un lugar de la Mancha, de cuyo nombre no quiero acordarme, no hace mucho tiempo que vivía un hidalgo de los de lanza en astillero, adarga antigua, rocín flaco y galgo corredor.