Reed, who lost to Jonas Blixt in the opener, never trailed during the match, putting Casey away with a clutch par on 16 and a two-putt birdie on 17.
The 16-man Match Play field is divided into four groups of four, with players competing in round-robin matches on Wednesday, Thursday and Friday. The top two players from each group will advance to the single-elimination bracket, which begins Saturday.
With his victory Thursday, Reed improved to 1-1 this week – the same record as the other three players in his group, Casey, Blixt and Jamie Donaldson (who defeated Blixt, 3 and 2).
Reed, the only American in the field, will play a win-or-go-home match Friday against Donaldson, who secured the clinching point for the Europeans at the Ryder Cup last month.
Meanwhile, defending champion Graeme McDowell suffered a rare match-play defeat, falling, 2 and 1, to red-hot Mikko Ilonen. The loss was just McDowell’s third in his past 18 matches at this event. Four down through 10 holes, McDowell cut his deficit to 1 down with three to play before Ilonen closed him out. Including concessions, the Finnish player recorded 11 3s in 18 holes played.
McDowell’s Ryder Cup partner, however, continued to roll at London Golf Club.
Victor Dubuisson, who went 2-0-1 at Gleneagles, continued his sterling form at the World Match Play, downing Shane Lowry, 3 and 2, to earn his second victory in as many matches. He has already secured a spot in the quarterfinals.
In other matches:
• Top-seeded Henrik Stenson was 2 down at the turn against Francesco Molinari, but he shot 7 under on the inward half to record a 2-and-1 victory. Tough draw for the Italian – he shot a bogey-free round of 7 under, yet still lost.
• Joost Luiten improved to 2-0 this week, after his 4-and-3 win over Alexander Levy, who won last week’s rain-shortened Portugal Masters.