Tuesday marked the first trading day of 2018, and the stock market largely started out where it left off before the New Year's holiday. A gain of roughly 100 points for the Dow Jones Industrials was actually the least impressive rise among major market benchmarks, with broader measures climbing from 0.8% to 1.5% on optimism for the coming year. Yet even though a combination of solid economic conditions, positive momentum in Washington, and a lack of worrisome new geopolitical issues sent markets higher, some stocks lost ground to begin the year. Tesaro (NASDAQ: TSRO), Archrock (AROC -1.14%), and Windstream Holdings (WINMQ) 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.

Tesaro takes a double hit

Shares of Tesaro fell 9% after the pharmaceutical company got negative reviews from two separate stock analysts. Piper Jaffray lowered its price target from $117 per share to $80, noting that extremely high expectations for its Zeluja cancer treatment might need to come down in order to reflect the realities of the market. Meanwhile, analysts at Cowen took their price target down from $125 to $80 per share, with similar statements including the potential for a competing drug in the space to pose a threat to Zeluja's revenue growth later in 2018 or early next year. Both analysts kept their ratings unchanged, but at neutral and market perform, respectively, neither has a lot of confidence in Tesaro's prospects.

Tesaro corporate logo.

Image source: Tesaro.

Archrock looks to combine with its limited partnership

Archrock stock declined 5% in the wake of the company's decision to acquire all of the outstanding units of its related master limited partnership, Archrock Partners (NASDAQ: APLP), for just over $600 million. Under the terms of the agreement, Archrock Partners investors will get 1.4 shares of Archrock for every partnership unit they own. CEO Brad Childers said that the combination should help Archrock's overall capital strength, allowing for greater dividend coverage and reduced capital costs. Yet despite the company saying the acquisition would be immediately accretive, shareholders weren't necessarily happy with Archrock giving MLP investors a big premium for their units, as Archrock Partners' 16% rise on the day suggests.

Windstream keeps sinking

Finally, shares of Windstream Holdings lost 4%. The telecom company was one of the worst performers in the market in 2017, as the suspension of its dividend shocked income investors who had long relied on the company's dependable payouts. Across the industry, adverse trends like cord-cutting are threatening the business models of the regional telecom specialists, many of which sought to double down in the increasingly obsolescent areas in which they had previously focused. Windstream hopes to be able to restructure itself and evolve beyond failing businesses, but investors don't have much confidence in the company's ability to accomplish that goal in the near future.