A goal either side of half-time from striker Robin Quaison, and a long-range effort just after the break from youngster Erkan Eyibil, sealed the Blues’ fate and ensured centre-back Lewis Gibson’s goal was merely a consolation.
After a rusty showing earlier in the 1-0 defeat to Sevilla, in which manager Marco Silva fielded a virtually full-strength team, the boss made seven changes for the encounter with Mainz, and it almost paid dividends straight away.
The Blues started the brighter, with both James McCarthy and Seamus Coleman managing early efforts on goal, albeit not forcing saves from goalkeeper Robin Zentner.
And twice Everton should have taken the lead just before the break, but Theo Walcott first dithered on the ball when through on goal, before Tom Davies wasted a possible counter-attack by passing to an offside Kevin Mirallas.
They paid for their profligacy seconds later, as Mason Holgate’s lazy attempt at intercepting Jean-Paul Boëtius’s ball played Quaison in on goal, and he made no mistake as he rounded keeper Jonas Lössl before slotting into an empty net.
Eyibil doubled the lead for Mainz, who had been beaten 5-0 by Sevilla shortly before this game, with a strike from just outside the box which Lössl could do little about.
Gibson headed in Kevin Mirallas’ corner minutes later, but another long-range goal, this time from Quaison, restored Mainz’s two-goal lead on 59 minutes.
Despite fielding a significantly weaker side than against Sevilla, the lack of strength in depth about Everton’s side was made painfully obvious in a rather pitiful display.
With just 12 days left before the transfer window shuts, this was another harsh reminder of the amount of work left for Silva and director of football Marcel Brands before the 2019-20 season kicks off away to Crystal Palace on Saturday, August 10.
Everton team (4-3-3): Lössl; Digne (Foulds 31’), Gibson, Holgate (Pennington 31’), Coleman (Connolly 31’); Schneiderlin (Hornby 54’), McCarthy (Adeniran 31’), Davies; Mirallas, Walcott (Gordon 31’), Broadhead.