Never won a European trophy, but he did lead us to an unbeaten league season (a clear proof of tactical ineptitude).
When it comes down to it, your definition of "great coach" is "wins lots of trophies" - except when it comes to Arsène Wenger who was just in the right place at the right time so it doesn't count.
As opposed to, say, Jose Mourinho who inherited a Chelsea side that had been evolving under various managers for several years, and a ream of blank cheques, and won the league playing a bog average defensive minded 4-3-3 with an incredibly strong squad.
Or Ferguson who happened to stumble upon the best single generation of youth players in England in the last fifty years, but in recent years has had title-winning sides repeatedly ground to mincemeat by Barcelona in Europe.
I'm not underrating either of the above as managers just pointing out that every trophy is the result of a multitude of factors.