adverb/a ˌmedjo ˈɡas/
at a leisurely pace; not at full speed
“le había valido navegar a medio gas y apretar puntualmente cuando fue algo exigido por Carreño y Tsitsipas” — going at a leisurely pace and squeezing the throttle when Carreño and Tsitsipas demanded something from him had worked in his favour.
Literally, “at half gas”.