Montgomerie is now 25 places outside world golf's top 50
Colin Montgomerie will definitely miss next month's Masters after he slipped to 75th in the latest world rankings.
Players not already qualified for Augusta needed to climb into the world's top 50 when the rankings were published on Monday.
Montgomerie needed a top-four finish at the Miami WGC-CA event this month to get back inside the top 50 but fell a long way short and took this week off.
The 44-year-old will miss the Masters for only the second time in 17 years.
Justin Leonard, Soren Hansen and Peter Lonard all made it into the top 50 on the eve of the cut-off and will line up at Augusta on 10 April.
Montgomerie has known for some time that his chances of appearing at Augusta this year were slim.
He eventually finished in a share of 65th place in Miami, effectively ending his hopes.
Northern Ireland's Graeme McDowell (61st in the rankings) and Wales' Bradley Dredge (69th) will also have to watch the Masters from the sidelines.
However, England's Nick Dougherty will be in the hunt for the Green Jacket, despite the latest rankings placing him just outside the top 50.
Dougherty's top-eight finish at last year's US Open, plus his top-50 ranking at the end of 2007, are enough to qualify.
Paul Casey, Luke Donald, Ian Poulter, Justin Rose and Lee Westwood are the other English players confirmed for the Masters field, while former winners Ian Woosnam and Sandy Lyle will boost the British contingent.
Earlier this year, Masters organisers offered three special invites to players outside the top 50.
Liang Wen-Chong (China), Prayad Marksaeng (Thailand) and Jeev Milkha Singh (India) all received the nod to compete in January.
Masters tournament chairman Billy Payne said the trio were "outstanding representatives" of their countries.
"We think the interest in golf in each country will heighten when these players compete in the Masters," he added.