The American added a Rolex Series victory at the BMW PGA Championship to his win at Austin Country Club as he finished a career-best second on the 2021 Rankings on the DP World Tour.
And upon his return to the scene of his maiden World Golf Championships win, Horschel claimed a 3 & 2 victory over fellow Rolex Series champion Min Woo Lee in Group 12.
The Australian won the first with a birdie but that would be the only time he led as Horschel won the next two with pars and birdied the sixth and eighth as he reached the turn 2 Up.
Further gains on the tenth and 13th put him four ahead, with Lee's win on the 14th only delaying the inevitable.
"Solid round of golf today," said Horschel. "Didn't do anything special.
"Min gave me a few holes which in match play we're always happy to get. After that I felt like I built a lead, it was just play smart, do the right things, give myself opportunities to make birdies. And then sort of make Min have to do something special to fight back."
There's something about Austin.— WGC-Dell Technologies Match Play (@DellMatchPlay) March 23, 2022
Six consecutive wins at ACC for our defending champ. pic.twitter.com/yTYiM5Adan
Thomas Pieters was another winner in Group 12 as he claimed a 2 &1 victory over Tom Hoge.
The big-hitting Belgian needed just two birdies to sit 4 Up after five and he was 5 Up after eight and seemingly in total command.
Hoge then claimed five birdies in six holes from the ninth to trail by just one but Pieters made a gain on the 15th and closed the match out on the 17th.
"I've never won my first round and then you're kind of coming from behind," said Pieters. "I think the percentage of getting through is very, very small if you don't win the first match. It's nice to have won this one and kind of build on that."
A birdie on the first and par on the third put the South African 2 Up but Hatton birdied the fifth and seventh and the pair could not be separated at the turn.
The Englishman then birdied the tenth, won the 11th with a par and another birdie at the 15th put him 3 Up with three to play.
"Christiaan definitely played better tee-to-green today," said Hatton. "I've got the putter to thank for today. I holed so many putts.
"It's a golf course that doesn't suit my eye at all, so obviously it's nice to hole putts today and get the confidence there on the greens."
Si Woo Kim beat Daniel Berger 2 Up in the other match in Group 13.
A ragged tee-shot from Fleetwood handed Fitzpatrick the first but the Yorkshireman returned the favour on the next and while he birdied the fifth, a bogey on the seventh saw the duo turn All Square.
They exchanged holes from the 11th to the 14th but back-to-back birdies put Fitzpatrick 2 Up before Fleetwood holed from 23 feet on the 17th to take it up the last.
The third Englishman in Group Five, Ian Poulter, lost 2 & 1 to Scottie Scheffler.
Irishman Seamus Power was 2 Up at the turn against Sungjae Im in Group Four with the help of a bogey-bogey start from his opponent.
The South Korean trimmed the gap at the tenth but Power made four birdies in a row to win 5 & 4.
"It's nice to get a point on the board," said Power. "It's my first time playing here so I wasn't sure what to expect but one for one, so it's a good start."
Patrick Cantlay and Keith Mitchell finished All Square in the other Group Four match.