Shares of Under Armour ( UAA) were sinking over 4% during afternoon trading on Thursday following a cautionary note from Susquehanna.

Susquehanna analyst Sam Poser argues that while sales of the company's recently released Curry 4 basketball shoes have been good, they are "not good enough."

Poser contends that "incremental sales" at Kohl's ( KSS) , DSW ( DSW) and Famous Footwear are not robust enough to offset the lost sales from the likes of Sports Authority, as larger retailers like Dick's ( DKS) plan down Under Armour products because of poor product segmentation.

"SportScanInfo (SSI) data indicates that ~34% of the UAA apparel styles carried in the moderate channel made up ~84% of the sales mid-March through May," he noted. "We recognize the aforementioned ratio is not unusual. However, the 34% of the styles that make up 84% of the business are carried in the athletic channel (Not Segmented)."

Retailers will begin to planning down their Under Armour business because they "do not want to get caught in a promotional free-for-all which is likely to occur when retailers such as Kohl's start discounting," he added.

What's Hot on TheStreet

Beware Tesla fanboys: Tesla (TSLA) burning money, but shareholders are the likely ones to blister and feel the pain. The standard 90-day corporate equity lockup period for Tesla, following its $402.5 million stock sale of March 16, ends Thursday TheStreet reports. As a result, Tesla will be free to conduct another stock offering as soon as Thursday, which is a real possibility given the electric car company's debt situation, partly due to its Solar City investment, and need for additional cash. Any new issuance the company may seek would likely need to take place before July, which is when Tesla issues its quarterly report on car sales. Alternatively, an offering could come in late August after Tesla issues its quarterly financial report.

Shares could start to come under pressure.

Mining stocks get whipped: Global mining stocks found themselves in a hole Thursday TheStreet reports, after South Africa's government said that at least 30% of domestic mining assets should be black-owned even if previous black owners sell their stakes. South African-exposed mining companies fell sharply in the wake of the announcement. London-listed Anglo American plc (AAUKF) tumbled 4.4% to 1,013 pence ($23.87) a share, South32 Ltd fell 4% to 158 pence, BHP Billiton plc (BHP) was down 2% to 1,155 pence, Rio Tinto (RIO) fell 2% to 3,079 pence and Glencore plc (GLNCY) fell 2.6% to 279.2 pence. South African gold producers were hit even harder. Sibanye Gold Ltd. (SBGLF) plummeted 6.7% to 1,562 South African rand ($121.38) and AngloGold Ashanti Ltd. (AU) fell 4.8% to 14,015 rand.

Amazon eyes a new prize: Amazon (AMZN) may be preparing a deal to buy Slack Technologies in a deal that could value the messaging startup group at more than $9 billion, TheStreet points out. With Microsoft's (MSFT) deal for LinkedIn being well-received, this deal seems logical for an Amazon that is aggressively expanding into the cloud.

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