KANSAS CITY, Mo. -- The Detroit Tigers got a glimpse of a possible rival in future AL Central races.
This season's champions got knocked around against a Kansas City lineup featuring four rookies, and lost 10-2 to the Royals on Tuesday night.
"I think they've been dangerous the last couple of months," Tigers manager Jim Leyland said. "That's not to say they weren't dangerous before, but they are really dangerous right now. This is a young team that is going to be really dangerous in the near future. That's an impressive team."
Hosmer's five-hit game was the first by a Royals player since Billy Butler on July 27, 2009.
"He looks like he's got a chance to be a really special player and he's a two-way player," Leyland said. "He's a good defender as well. He's going to be a big hit in this league for a long time. He's got to be a top candidate for rookie of the year."
Mendoza, the Pacific Coast League pitcher of the year after going 12-5 with a league-best 2.18 ERA, held the Tigers to two runs, one unearned, and six hits in seven innings in his first big league appearance since April 19, 2010.
Mendoza (1-0) got his first major league victory since Aug. 3, 2008 while with the Texas Rangers, an 8-4 decision over Toronto.
Hosmer's three-run homer off Brad Penny highlighted a six-run fourth inning to put the game out of reach.
"I made some pitches in bad locations." Penny said. "The curveball for the Hosmer homer was a bad pitch. Everything I threw they hit hard. It's frustrating but I'm going to keep working and keep going back out there. Tonight I didn't give us much of a chance to win. Hosmer is going to be a good player. He already is."
Alex Gordon started the bottom of the first with his fifth leadoff homer of the year.
Penny (10-11) allowed seven runs on 10 hits in four innings to lose for the first time since Aug. 28.
"He made some bad pitches and they got whacked," Leyland said. "Those guys are really aggressive and they are feeling good about themselves and they deserve to. He was leaving hittable pitches up where they could hit them and those guys are going to hit them."
Austin Jackson's double in the fifth scored Andy Dirks with the first Detroit run. Ramon Santiago, who reached on second baseman Johnny Giavotella's error, scored on Delmon Young's sacrifice fly in the seventh for the other Tigers run.
While the Tigers have clinched the AL Central, Leyland said his club is "still fighting for home-field advantage" for the playoffs. ... Leyland said he would rest 1B Miguel Cabrera Wednesday. "He deserves it," Leyland said. "We're going to get home late and he'll play the rest of the way out." ... Butler was scratched from the Royals lineup with the flu. Maier replaced him, making his first career start at DH. ... Royals closer RHP Joakim Soria remains sidelined with a strained right hamstring. He has not pitched since Sept. 11. ... RHP Felipe Paulino will make his third start against the Tigers on Wednesday. He is 1-0 with a 2.63 ERA against Detroit. The Tigers will start right-hander Max Scherzer, who went to the University of Missouri and was the 2005 Big 12 Conference pitcher of the year as a sophomore.