One of the best episodes of the entire series, although the plot wasn't huge: Just a couple friends playing football, it was some of the best writing I've seen in a while. I really do have to commend Ira Ungerleider here, she wrote this episode perfectly.
I wouldn't call this episode underrated but it definitely deserves some more recognition. This episode kept me intrigued throughout the whole thing, not to mention it was funny. The classic Ross vs. Monica sibling rivalry was hilarious.
It was also great aftermath after the Chandler & Janice fallout, considering any scenes between them this season were dreadful. Rachel was the one that stole the show here though. From her going "really long" to her making the touchdown in the end, she was really great here.
The end was pretty funny and it was a perfect conclusion, it still leaves the fans debating on who really won the football game and who was in the wrong there. Great episode of Friends, instant classic.