Definition of "assured"

Youngster Townsend caught the eye on the wing, with his fantastic goal capping a classy performance, while Danny Rose continued his rapid development with an assured display at full-back.

2011 December 15, Marc Higginson, “Shamrock Rovers 0 - 4 Tottenham”, in BBC Sport‎

What thinkſt thou man, ſhal come of our attempts?For euen as from aſſured oracle,I take thy doome for ſatiſfaction.

c. 1587–1588, [Christopher Marlowe], Tamburlaine the Great. […] The First Part […], 2nd edition, part 1, London: […] [R. Robinson for] Richard Iones, […], published 1592; reprinted as Tamburlaine the Great (A Scolar Press Facsimile), Menston, Yorkshire, London: Scolar Press, 1973, Act II, scene iii