Greinke, dealt by the Royals in a major trade after the 2010 season, was moved by the Brewers to the Angels on July 27 because he's coming up on free agency.
"I've known Zack a little bit. Not the way guys here do, but the way things ended I know wasn't great, but he won a Cy Young [Award] for them and I'm sure there are lot of good memories still for him," right fielder Jeff Francoeur said.
"And for them, they're in the middle of a big pennant race, so obviously it'll be a big start for him and for that team. So it'll be a lot of fun. It's always good facing good guys like that because you know they're going to challenge you and come after you."
The Angels, while running third in the American League West, are in the Wild Card hunt. Greinke, since joining them, is 5-2 in nine starts and, including his Brewers record, is 14-5 with a 3.68 in 30 starts.
When Greinke started for the Brewers in June, he was greeted by leadoff batter Alex Gordon's home run. But that was the only run he gave up in a tight duel with Royals starter Luis Mendoza.
Francoeur remembered that Greinke was tough.
"Back door sinkers -- throwing the whole kitchen sink at you," Francoeur said.
The Royals broke a 1-1 tie against Brewers reliever Francisco Rodriguez on Billy Butler's RBI single in the eighth inning to win.
Being able to watch Greinke over a long period as Butler and Gordon did as teammates really didn't give them an advantage, in Butler's view.
"Nobody has an advantage on Zack because he's so good," Butler said.
Greinke and Royals starter Jeremy Guthrie, who is 4-0 with a 1.70 ERA in his last seven starts, aren't the only gate attractions for that game. It's also Armed Forces Night and the first 20,000 fans will receive a KC camouflage cap.