Genie Bouchard and Mason Rudolph could be getting serious … the tennis star showed up to the Steelers game Sunday with friends to cheer on her new beau!!!

We broke the story … Genie and the Steelers backup QB kicked off a romantic fling recently — and clearly, the fire is still burning hot.

‘Cause just weeks after 26-year-old Genie was spotted out and about near Rudolph’s Pittsburgh-area home … she headed to 25-year-old Mason’s game against the Titans in Tennessee.

And, while Mason didn’t play in the win (he’s backing up a healthy Ben Roethlisberger this season) … didn’t seem Genie minded too much — check out her smile!!!

Yeah, looks smitten to us!!

Neither Genie nor Mason has gone public with the relationship yet … but posting pics from games means we could be getting close to IG offish any day now.

Congrats on the young love!