Since Kevin Plank founded Under Armour (NYSE:UAA) in 1996, the outspoken CEO has seemed to embrace the role of the underdog. 

That role has certainly served him well. Since its IPO in 2005, the young performance apparel company has managed to increase annual revenue from just $281.1 million to a staggering $1.835 billion in 2012.

Let's take a look, then, at five quotes from Plank in an effort to see what makes both he and his company tick:

On starting a business
"There's an entrepreneur right now, scared to death, making excuses, saying, 'It's not the right time just yet.' There's no such thing as a good time."

And Plank would know. He started Under Armour out of his grandmother's basement with $40,000 in credit card debt -- an admittedly risky move -- and $17,000 in seed money from a flower business he ran in college. Still, his "no excuses" attitude gave him the guts to pursue what he rightly believed was a yet-to-be-filled niche in moisture-wicking athletic gear, and that move paid off in a big way.

Under Armour Stock

Under Amour CEO Kevin Plank. Image Source: Wikimedia Commons.

On pursuing sustainable growth
"One of our first customers asked me how big we want to be. I said I want to be really big. Later, it bothered me that I answered that way. Now I say I just want to be a great company."

It's safe to say Plank is well on the way to achieving his goal of making Under Amour really big; last quarter marked Under Armour's 14th consecutive quarter of maintaining at least 20% top-line growth in its flagship apparel sales and the 12th consecutive quarter of more than 20% year-over-year growth in total revenue. What's more, the company has maintained its goals of sustaining this 20% annual revenue growth for the foreseeable future.

The second part of that quote, however, is far more important to Under Armour investors. After all, it's a great feeling to know Plank recognizes that growth for the sake of growth can be toxic over the long run if he doesn't build a great business to back it up.

On diversifying revenue streams
"As we've grown to where compression was only 14% of our business in 2012, we've continued to move away from dependence on cold weather with more focus on providing a broad range of fabrication, and we even decided that cotton didn't have to be the enemy."

To be sure, Under Armour's "charged cotton" line of clothing surprised many people given the company's old "Cotton is the enemy" slogan. Still, the fact remains that it should help Under Armour's clothing to become more attractive to a wider audience without sacrificing its token innovation -- charged cotton clothing apparently dries five times faster than conventional cotton and wicks moisture by interweaving cotton with Under Armour's own synthetic fabrics.

Besides, as Plank also noted in an interview at the time with Forbes, "We looked into our customers' closets and found 30 T-shirts. Four were synthetic, and the other 26 were cotton."

On entering a land of giants
"Basketball is a great example where one company dominates 90 plus percent of the market. And what I can commit to you is that I'm not going to make predictions on exactly how much market share, but I would much rather be sitting where we are because it's coming. We will take market share."

Naturally, that "90 plus percent" dominator in the massive basketball shoe market is none other than Nike (NYSE:NKE), a largely unmatched foe that pulled in more than $13 billion in footwear revenue in 2012 alone. In retrospect, that makes Under Amour's $81 million in footwear revenue last year seem downright minuscule.

However, while many analysts have remained skeptical of Under Armour's perceived slow launch into footwear, remember that the company is only just getting started. In fact, Plank recently reminded us that he has purposely remained cautious and methodical in entering the already-crowded athletic footwear space: In 2006, it introduced football cleats, followed by baseball cleats in 2007, training shoes in 2008, running shoes in 2009, and, finally, 2010 saw the launch of Under Armour's first basketball shoe.

And that reminds me of the final quote...

On keeping your eye on the prize 
"You will hear about us one day."

In Under Armour's early days, Plank used to include this simple statement on a Christmas card he would send to Nike founder Phil Night every year. 

Call it what you will, but this is exactly the kind of confidence Plank has used to turn Under Armour into a multibillion-dollar business -- and a business he obviously cares for deeply. In the end, I'm apt to believe betting against this loyal founding CEO is a terrible idea, and that's just one of many reasons Under Amour remains one of my favorite long-term investments.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.