Of those mentioned, Michu and Drinkwater stand out for me. Michu and his hand gesture while celebrating was a common sight for one season, then he fell off a cliff. For the Leicester title season everything Drinkwater hit seemed to fall perfectly into the path of Vardy to score. After that season he disappeared, unlike Vardy.
Kevin Phillips had one season hitting 30, he never managed half that again. Daniel Sturidge hit over 20 one season, don’t think he managed double figures again as injuries meant he barely managed to play half the fixtures.
Better a one season wonder and be remembered than a no season wonder and be forgotten, such as world class talents in Davor Suker, Pierluigi Casiraghi, Andriy Shevchenko, Brian Laudrup, Fernando Morientes. When Chelsea got two of those (Laudrup and Casiraghi) they were fancied to do well...unlucky it didn’t work out for various reasons. Kagawa at United was another who didn’t do it for whatever reason...with Dortmund (and Japan) he looked imperious. United have got very little out of top quality over the last decade, Di Maria probably top of the pile.
Wouldn’t include Michael Keane as a one season wonder. He just played in a solid, ultra defensive system that didn’t expose his limitations. Burnley’s defence was better the season after he left, so it wasn’t the individual it was the system. He hasn’t regressed since coming here, he has just been exposed a lot more.
Not really a one season wonder, more a few months wonder, Theo Walcott when he arrived on the scene at Southampton looked the business. Every club clamouring after him. Taken to a World Cup. Never kicked on after that.
In terms of having a purple patch, the ultimate has to be Toto Schillachi. Did nothing of note before the 1990 World Cup, five weeks of top finishing, then did nothing of note after the 1990 World Cup. He totalled roughly 35 goals in Italy’s top flight. He spent 7 seasons in the lower divisions, then had one season in Serie A before the 90 World Cup, was a fringe player after that.