The 24-man field will play at Spain's Costa del Sol, where the European Tour returns after a one-year absence. The tournament, which starts Thursday, features five of the top six players.
Donald won the Accenture World Match Play title at Arizona in February, never falling behind in any of his six matches. He is looking to become the first player to win both match-play tournaments.
Given his success in the match play format at recent Ryder Cups, the No. 2-ranked Donald is the man to beat this week. However, Westwood has won his last two tournaments — in Indonesia and South Korea.
"My confidence is very high right now," said Donald, who has finished in the top 10 in 13 of his last 14 events. "I've been playing very consistently now for a good six months, and I think the win at the Match Play really elevated that confidence level.
"Obviously, I enjoy match play, my record is very good. My record in Ryder Cups, Walker Cups, the Match Play event this year, they speak for themselves. I enjoy the challenge of that one-against-one over 18 holes."
Westwood knows all about the caliber of Donald's match play — the two paired for the 2010 Ryder Cup to devastating effect, thrashing Tiger Woods and Steve Stricker 6 and 5 in the second day's opening foursomes.
He's not surprised to see Donald move up the rankings this year.
"He hits the ball straight off the tee, his iron play is nice, he's got a great short game and he's a nice putter," Westwood said Wednesday. "He's very reliable."
No. 3-ranked Martin Kaymer, who split with his Scottish caddie Craig Connelly on Sunday, joins the Englishmen in the strong field and there are enough points to allow the German to move back to the top of the rankings, too.
Kaymer lost to Donald in the final at Arizona and acknowledged the talent of the world's top two.
"I think the perfect player at the moment would be the long game from Lee Westwood and the short game from Luke Donald," Kaymer said.
Fourth-ranked Phil Mickelson is the only player in the top six not featured at the Finca Cortesin course near Marbella, where there is a total prize purse of $4.8 million. The winner will receive $1.14 million, the highest amount on the European Tour outside of the majors, World Golf Championship events and the Dubai World Golf Championship.
The four current major champions will compete — Louis Oosthuizen (British Open), Graeme McDowell (U.S. Open), Kaymer (U.S. PGA) and Charl Schwartzwel (The Masters).
The field has been divided into eight groups of three, with the top two in each going through to the knockout stages on Saturday and Sunday. Fierce winds and heavy rain swept across the course on Wednesday and the inclement weather is expected in the south of Spain all four days.
"To be the World Match Play champion for almost two years has quite a nice ring to it," said Fisher, who will not start the defense of his title until Friday. "I've got good memories of this place, so hopefully they'll come flooding back. I'll just try to do the same things I did two years ago."
Westwood is joined by Denmark's Anders Hansen and Australia's Aaron Baddeley, while Oosthuizen and McDowell are in the same group with Jhonattan Vegas of Venezuela. Kaymer was drawn with Korean pair Y.E. Yang and Noh Seung-yul.
Denmark's Thomas Bjorn flew to Spain as first reserve, but returned home Monday following the death of his father after a long illness.
The event moved to Spain for the first time in 2009, having previously been played since 1964 at Wentworth, England.