In the present work, the subsurface microstructure evolutions of Ti-29Nb-14Ta-4.5Zr (TNTZ) during high speed-sliding wear against Ti-6Al-4V extra-low interstitial has been studied in detail. Its correlation with surface features characteristics is also discussed. Progressive substructure development and mechanical twin formation have been proposed to be the main subsurface deformation mechanisms. The microstructure of the subsurface deformed regions consists of both primary and secondary twins holding ∑3:{112}<111> and ∑11:{332}<113> orientation relationships even at the early stage of sliding. Surprisingly, examinations indicate that an ultra-fine grained metal mixed layer is formed underneath the wear track, the extent of which increases in relation to the sliding distance. The latter has been justified considering the progression of primary mechanisms under a high imposed strain rate and the resulting tangential force. Despite the previously reported results for the same couples, the tribological performance of the TNTZ experimented alloy is significantly improved. This is well discussed relying on the increased subsurface hardenability of the alloy under the high-speed wear regime, which effectively supports the superficial oxide layer and prevents the premature micro-crack formation.