Inspired by the famous result of Rosenthal, that a subspace of L_1 that does not contain l_1 is superreflexive, we define property (R) of Banach spaces -- a Banach space has (R) if and only if every weakly precompact (that is bounded not containing a sequence equivalent to the l_1 basis) subset is relatively super weakly compact (this is a localisation of superreflexivity in the same way as relative weak compactness is a localisation of reflexivity). We will investigate property (R) and show that Lipschitz-free spaces over superreflexive spaces enjoy it, proving some new non-embeddability results. The proof is based on the proof of weak sequential completeness of such spaces by Kochanek and Pernecká and an appropriate version of compact reduction in the spirit of Aliaga, Nous, Petitjean and Procházka.