The 44-year-old five-time major winner from San Diego admitted he was disappointed he would miss the knockout event at TPC Harding Park.
Mickelson, whose last win came with his Open Championship triumph at Muirfield in 2013, said: “I’m really happy with the new format and TPC Harding Park is a terrific setting for match play, so it’s unfortunate that I won’t be able to play this year.”
Last year’s Volvo World Match Play Championship winner Ilonen joins the field and is ranked 62 ahead of the draw.
Defending champion Jason Day is ranked seventh for this year’s event, where the world’s top 64-ranked players take part. The action which gets under way on Wednesday.
The draw for the tournament which was first introduced in 1999 takes place later on Monday.