Montgomerie failed to qualify for the 2008 Masters in April
Scotland's Colin Montgomerie has dropped out of the world's top 100 for the first time since 1990.
Montgomerie, 44, came 58th at the Wales Open to slide from 95th to 102nd in the rankings and is almost certain to miss out on automatic Ryder Cup selection.
The Eight-time European number one lies 57th in the Ryder Cup world points list and 38th in the European table.
Without a top-40 finish in strokeplay since January, Montgomerie is ranked two places above Darren Clarke.
Northern Irishman Clarke's fourth place at Celtic Manor maintains his climb through the rankings after being outside the top 200 at the start of the year.
Montgomerie is set to miss out on one of the 10 automatic slots in Europe's Ryder Cup team that will defend the trophy in Valhalla in September.
But he will focus on the six weeks immediately after the Open in July, the period Europe's captain Nick Faldo says will be key to gaining one of the two wildcard spots.
Meanwhile, Justin Rose has replaced Sergio Garcia as Europe's only member of the world's top 10.
The 27-year-old Englishman finished in a four-way tie for second at the Memorial Tournament and would have leapt to a career-best third if he had won.