LONDON -- Picking good stocks is quite an art, but what about bad stocks? For the last few months, I've been working through the FTSE 100, looking for great opportunities. Here are five companies that didn't make the cut.

British Sky Broadcasting (SKY)
In January, I described British Sky Broadcasting as a Premier League investment. I'm not so confident now. The difference is that it now faces table-topping competition in the form of BT Group. Its new service, BT Sport, offers 38 Premier League matches free if you sign up to its superfast fiber broadband service, BT Infinity. That is still dwarfed by the 116 matches BSkyB offers, but it's a serious challenge, and it risks dragging BSkyB into a price war. BSkyB's share price is down 13% since the news broke, so I'm not the only one worried. BSkyB is now down 5% over the past two years against a 14% rise for the FTSE 100. Like Manchester United after the departure of Sir Alex Ferguson, it now faces a much tougher battle to maintain its dominance.

Fresnillo (FRES -1.31%)
I was skeptical about silver and gold miner Fresnillo in January, and my fears appear to have been realized. The share price had enjoyed a glittering five years, rising 160% to £17.20, but I thought it looked overvalued at 27 times earnings. Despite what management calls "a strong start to 2013," hitting all its production targets, the share price has now plummeted to just £10.76. There is little wrong with the company itself. The world's largest primary silver-producer has zero debt, for example. But precious-metal prices have lost their luster, with the six-month silver price down 33%. This has knocked that valuation to just 17 times earnings, which some investors might see as a buying opportunity. I'm not one of them.

Antofagasta (ANTO -0.62%)
Antofagasta is another miner whose share price is heading underground. And once again, it has done all the right things, boosting copper production by nearly 13% year on year, only to be hit by events beyond its control. The copper price has fallen more than 10% since I looked at this stock in early January. Antofagasta's first-quarter results, just released, show group revenue down 15% to $1.5 billion and adjusted earnings down 29% to $782 million. Strike action and the falling gold price didn't help. Copper miners are a play on the global economy, but that looks to be in poor health right now, kept alive by the ever-diminishing returns of easy monetary policy. If you're feeling more bullish than I am, you might be tempted by Antofagasta's lowly valuation of 10 times earnings, down from more than 15 times at the start of the year.

Man Group (LSE: EMG)
Hedge funds have never been my cup of tea, so it's hardly surprising that Man Group isn't to my taste. But the market thinks differently right now. After years of weak and wimpy performance, it is starting to man up with a vengeance, rising 73% in the last six months to £1.32. The recovery was well under way when I examined this stock in late February, but I decided it was too volatile for my needs. It is still down 46% over two years, for example. Last quarter saw client withdrawals totalling $3.7 billion (against $2.8 billion of inflows), reducing total funds under management to $55 billion. Loyal Man Group shareholders have had some fun lately, but this company still has a lot to prove, especially regarding fund performance.

Amec (LSE: AMEC)
Investors in energy and engineering consultancy Amec have had lean pickings lately. Its share price is up a meager 6% over the past 12 months against a barnstorming 26% for the FTSE 100. Over two years, it is down 10%. Back in February, I thought the market was being a bit harsh on Amec, which had published full-year results showing profit before tax up 8% to £336 million and underlying revenue growth of 21%. Management was cautious about the future, knocking sentiment. April's first-quarter trading update showed a flat order book, although it had won new contracts in the North Sea, and recent acquisitions are bedding in well. It is a little harsh to include Amec in my bottom five. It is now nicely valued at 12.9 times earnings and yields 3.4%. But for me, this stock still doesn't sizzle.

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