Taylor Swift Standing on Business, Blazer and Miniskirt at Chiefs Game

Taylor Swift's ready to watch her man take care of business against the Denver Broncos ... pulling up to his Sunday afternoon game in K.C. in a biz-casual ensemble.

The singer-songwriter rolled into Arrowhead Stadium in a red and black checkered blazer, pulled over a low-cut black top ... with a tiny skirt matching her jacket.

Clearly, she's in her "No-Nonsense Era" ... preparing to watch her boyfriend Travis Kelce's team beat up on their division rival.

Of course, there's still a full game to be played ... but, the Chiefs have looked really strong recently -- including in last week's overtime win against the Tampa Bay Buccaneers.

T-Swift looked jovial at that matchup ... waving to fans and cheering her man on as he racked up his biggest game of the year -- pulling in a career-high 14 catches for 100 yards.

She's had a jam-packed weekend -- not exactly out of the ordinary when she's not touring -- going out to dinner Friday night with her famous friend Zoë Kravitz.

Sunday's for the beau however ... and this may be the last game she attends for a while, 'cause she goes back on tour this Thursday in Toronto.