Dick's Sporting Goods shares plummeted more than 18 percent Tuesday morning after the sporting goods retailer missed Wall Street expectations and lowered its 2017 outlook.

The stock opened at a low not seen since 2010.

Pittsburgh-based Dick's had hoped to benefit from rivals' bankruptcies, including those of City Sports and Sports Authority, but competition from specialty retailers like Under Armour and Foot Locker remains a threat.

The company recently launched a private-label clothing line, called Second Skin, that aims to compete directly with Under Armour's niche. But it's too soon to tell if the line will help boost sales. In the latest period, apparel was particularly weak for Dick's.

During the second quarter, Dick's said net income rose to $112.4 million, or $1.03 a share, from $91.4 million, or 82 cents a share, a year ago.

On an adjusted basis — excluding a previously announced corporate restructuring charge and income related to a contract termination payment — quarterly profit was 96 cents per share, 4 cents below estimates from Thomson Reuters.

Helped by the expansion of its store network, sales rose 9.6 percent to $2.157 billion from last year. Analysts, however, were expecting revenue to reach $2.161 billion, Thomson Reuters said.

Consolidated same-store sales rose 0.1 percent, far lower than the company's forecast of 2 to 3 percent growth and a Thomson Reuters forecast for 1.7 percent growth.

CEO Edward Stack called the current sporting goods marketplace "very competitive and dynamic."

Weakness in hunting and licensed sports apparel, among other factors, also hurt Dick's results, the company said.

"By design, we will be more promotional and increase our marketing efforts for the remainder of the year, as we will aggressively protect our market share," Stack said in a statement.

"We have updated our outlook to reflect these investments. We continue to believe retail disruption creates opportunities for us as we look long-term."

Dick's now expects to earn between $2.80 to $3 a share, on an adjusted basis, this fiscal year. Analysts surveyed by Thomson Reuters were calling for adjusted earnings of $3.09 per share.

Same-store sales for the year are now expected to be between flat to down at a low-single digit rate. In 2016, Dick's same-store sales rose 3.5 percent.

"Dick's is another example of Amazon becoming the new middleman," SW Retail Advisors' Stacey Widlitz said in an interview with CNBC. The apparel and accessories "specialty space is no different than a department store when your brands decide to wave the red flag and sell on Amazon."

"Here we go down the gross margin rabbit hole just in time for the holidays."

Dick's said it expects to open 43 new stores and relocate seven locations by the end of the year. The company opened 13 Dick's stores in the second quarter, growing its presence across California, Florida, Washington, Georgia and Tennessee.

While many retailers are seen shuttering stores, Dick's is betting that a growth strategy will pay off, and Stack on Tuesday said that "retail disruption creates opportunities."

Some are less convinced that Dick's can turn things around. According to UBS analyst Michael Lasser, the athleisure cycle seems to be peaking, and this will hurt the sporting goods retailer over time.

"DKS is operating in a tough sporting goods retail landscape," Lasser wrote in a note to clients last week. "While it's managing the environment better than its brick and mortar peers, it isn't fully immune from the external environment."

Recent reports from other sporting goods rivals, such as Hibbett Sports, Cabela's, Callaway Golf and Big 5 Sporting Goods, spell trouble in the industry, UBS said. All signs point to "puts and takes" on Dick's margins, especially as promotional activity increases, Lasser added.

As of Monday's market close, shares of Dick's Sporting Goods had fallen more than 34 percent in 2017.