When you're the top brand with dominant market share like Nike (NKE), financial resources become a distinct competitive advantage.
In the chart below, company disclosures show that Nike has nearly $3.8 billion in sponsorships/endorsements on its books, which is 25 times higher than Under Armour (UA). That accounts for a far greater percentage of sales for Nike, too, as you can see in the chart below.
Nike's financial obligations related to those sponsorships are also spread out over a longer time period compared to those of Under Armour, as this second chart shows. That's also a likely competitive advantage for Nike.