Hendriks makes his Royals debut Wednesday night against the visiting Minnesota Twins.
Ventura was initially scheduled to start but will rest his sore back, which bothered him in his last outing against Texas on Friday night. The rookie went 3-1 with a 2.56 ERA over his last five starts.
"Could he pitch tomorrow? Yeah, probably. Maybe," manager Ned Yost said. "But as a precaution we think it's smarter to go ahead and bang him one start and go from there."
In his place will be Hendriks (1-0, 6.08 ERA) who hasn't pitched in the majors since June 20 for Toronto. He's 12-2 with a 2.45 ERA over 23 games between Triple-A Buffalo and Omaha.
The right-hander was just 2-13 with a 6.06 ERA in 30 games for the Twins from 2011-13. Minnesota designated him for assignment in December and then he bounced from the Chicago Cubs to Baltimore before winding up with the Blue Jays, who dealt him July 28 along with catcher Eric Kratz in exchange for Danny Valencia.
"It'll be interesting. It could be really good or really bad," Hendriks said. "But I'm just going to go out there and pitch the same way I have. The way I'm pitching this year isn't the same way I was pitching last year, so hopefully I can catch them a little bit off guard."
Kurt Suzuki is the only current Twin to face Hendriks, hitting one home run in three at-bats.
The Royals (73-58) are seeking their 10th home win in 12 games after taking a 2-1 victory in Tuesday's series opener. Alex Gordon gave Kansas City a walkoff win with a two-run shot in the ninth.
Gordon has seven home runs over his last 19 games and 16 overall.
"Really didn't have any offense going all night and was able to muster up something, so that was great," Gordon said.
For Minnesota, Phil Hughes (14-8, 3.65) has a chance to tie Detroit's Max Scherzer and Rick Porcello for the AL lead in victories. Hughes has won four straight starts, limiting opponents to four runs over 27 1-3 innings while striking out 30.
"When you get on good stretches, everything's kind of working for you mechanically and your game plan, everything, just kind of falls into place," Hughes said.
That stretch includes a 4-1 victory over Kansas City on Aug. 16 when he yielded one run in 7 1-3 innings. He's 7-3 in 11 career starts against the Royals despite a 5.19 ERA.
Alcides Escobar, who singled ahead of Gordon's homer, is 5 for 13 off Hughes.
The Twins (58-73) have dropped three in a row and seven of 10. Tuesday marked Glen Perkins' first blown save on the road since the club's second game of the season on April 2 against the Chicago White Sox.
"I don't think anybody saw that coming," manager Ron Gardenhire said. "A bloop and a blast and a big walkoff for them."