The Masters Tournament is set to have its smallest field in 20 years when the year's first major championship begins next week at Augusta National Golf Club.

Four players were added to the field Monday via the Official World Golf Ranking, with the possibility of one more this week at the Houston Open. The winner, if not already invited, will get the last spot in the field that now stands at 87 players. That includes U.S. Open champion Brooks Koepka, who is not expected to play because of a wrist injury but has yet to officially withdraw.

This will be the first time since 2016 that the tournament field will be less than 90 starters. In 1998, 88 players began play. In 1991, 87 players took part.

First-timers Satoshi Kodaira of Japan and Dylan Frittelli of South Africa were among the top 50 in the world on Monday, along with American Chez Reavie and Australian Cameron Smith, thus qualifying via that invitation category.

Kodaira and Frittelli had moved into the top 50 earlier this year and stayed there at Monday's deadline. Reavie began the year ranked 95th and moved into the top 50 with a couple of strong performances, including a playoff loss at the Waste Management Phoenix Open. Smith needed to advance to the final 16 at the WGC-Dell Technologies Match Play Championship over the weekend to secure his spot.

England's Ian Poulter needed one more victory at the Austin, Texas, event to secure an invitation, finishing 51st in the rankings. The only other way into the Masters field is a victory this week in Houston.

Among those playing in Houston who are not in the Masters field are Ernie Els, Steve Stricker, Bill Haas, Poulter, Keegan Bradley, Brandt Snedeker and Charles Howell III.