Walker recovered from 3-7 and 12-13 down in the final game to win 12-15, 15-9, 15-3, 13-15, 15-13 against an improving opponent who became the first German to reach the semi-finals of a major tournament in the European Open in Kiel last month.
Walker's win means that only the extremely unlikely occurrence of both Australia's Rodney Eyles and New Zealand's Ross Norman reaching the semi-finals will push the Englishman out of the world's top eight.
A top-eight place should free Walker to play for his country in next year's world championships even if the threatened players' boycott of next month's English national championships takes place, though another nine players have added their names to the list of boycotters to make a total of 17.
In another close encounter, England's John Ransome, a qualifier, beat Austin Adarraga, the Australian-born world No 16 from Spain, 9-15, 15-14, 15-8, 5-15, 15-14.
Adarraga, characteristically, spent large parts of the match arguing with the referee and yet again appeared to be frittering away his considerable talent in dissent.Reuse content