The BMW Championship, which starts Thursday at the Nord-Eichenried course, will complete the 10 automatic qualifiers for Europe's defense against the United States next month at The K Club in Ireland.
European captain Ian Woosnam will round out his 12-man team with two picks shortly after the tournament ends Sunday.
Luke Donald, Sergio Garcia, Henrik Stenson, David Howell, Colin Montgomerie, Robert Karlsson and Paul Casey have all qualified. Padraig Harrington is on the cusp of qualifying, currently ninth overall.
The U.S. team was named after the PGA Championship 10 days ago.
The top five from the Ryder Cup world points list and the European points list make up the European team.
Olazabal is currently fifth overall and on the world list. But the Spaniard, who tied for third in the Masters in April, said he needed a rest and opted not to play this week.
'I must say he's left himself a little bit vulnerable,' Woosnam said Wednesday.
Olazabal, a veteran of the past six European teams, will keep his place if Montgomerie finishes outside the top 47 or Casey is not in the top two. But he is more likely to be 10th overall.
If that happens, Olazabal would lose his spot if Paul Broadhurst finishes in the top three, Johan Edfors is in the top two, or John Bickerton or Thomas Bjorn wins the tournament.
McGinley, who sank the winning putt at The Belfry in 1992, is 10th overall and could be knocked out if Broadhurst or Edfors finish first or second, or if Bickerton wins the event.
McGinley was on the team that beat the Americans 18 1/2 to 9 1/2 at Oakland Hills two years ago.