Rihanna is one A-lister who knows how to marry posh and sporty pieces together. This fall, one of her most casual cool-girl looks is trending, and we can't stop swooning over it. Enter: rugby shirts. With thick polo-style collars and preppy stripes, rugby shirts are the ultimate way to diversify your fall wardrobe. Whether you're a fan of street-style-approved looks or prefer elegant, rich-mom styles, rugby shirts are the way to go.