Monday was another good day for stocks, as major benchmarks continued their slow but steady ascent. Without much in the way of market-moving news on the geopolitical or macroeconomic fronts, investors largely focused on individual companies, especially in the wake of numerous earnings reports and other news items affecting key companies. Teva Pharmaceutical Industries (NYSE:TEVA), Intrepid Potash (NYSE:IPI), and Ensco (NYSE:ESV) were among the worst performers on the day. Below, we'll look more closely at these stocks to tell you why they did so poorly.

Teva gets a bad review

Shares of Teva Pharmaceutical Industries dropped 10% after the drug company got negative comments from a key Wall Street analysis company. Analysts at Morgan Stanley downgraded shares of Teva from equal weight to underweight, citing pressure on the company's generic-drug business and vulnerability to potential price cuts. With generic competition on the horizon for Teva's key best-selling proprietary multiple sclerosis drug, Teva faces attacks on multiple fronts. With a new price target on the stock of $16 per share, Teva could have further to fall before all is said and done.

Teva Pharmaceutical Industries logo.

Image source: Teva Pharmaceutical.

Intrepid gives back some gains

Intrepid Potash stock fell 16% as the fertilizer specialist also got an analyst downgrade. Professionals at UBS cut their rating on shares from neutral to sell, arguing that the potash fertilizer market remains under pressure from relatively low prices and that positive reaction to Intrepid's encouraging second-quarter earnings report might have been overdone. Shareholders seem to agree, but even with the drop, Intrepid shares are still up nearly 60% from where they started the year. Investors will have to wait to see whether a global economic recovery has a positive impact on fertilizer prices soon enough to help Intrepid clean up its balance sheet further and start growing again.

Ensco gets drilled

Finally, shares of Ensco finished down 6%. Most of the attention around the offshore driller lately has centered on its recent decision to acquire industry peer Atwood Oceanics (NYSE:ATW), doubling down on its bet that the energy sector will continue to rebound. Investors have responded to calls to reject the offer, arguing that the all-stock deal is overpriced and doesn't make sense in a challenging time for the offshore drilling industry. Activist investors have gone so far as to write an open letter to shareholders condemning the deal, and it will be interesting to see what happens once a special shareholder meeting actually happens.

Dan Caplinger has no position in any stocks mentioned. The Motley Fool owns shares of Atwood Oceanics. The Motley Fool recommends Teva Pharmaceutical Industries. The Motley Fool has a disclosure policy.