The stock market has a dirty little secret this year that too few investors are aware of: while the big S&P 500 index pushes its way to new all-time highs again this week, there's a very big chunk of the market that's not participating in the rally.

As I write, almost a quarter of the stocks in the S&P are actually down since the calendar flipped to January. That's some pretty sizable underperformance from a very big chunk of the market. And it means that it's not hard to own some "toxic" stocks in your portfolio right now ...

The good news is that you don't need to try and find the very best performers for 2017 to wring the biggest profits out of the market this year. All you need to do is avoid the worst ones.

So, to find the stocks to avoid in March, we're turning to the charts for a technical look at four you should consider selling here ...

For the unfamiliar, technical analysis is a way for investors to quantify qualitative factors, such as investor psychology, based on a stock's price action and trends. Once the domain of cloistered trading teams on Wall Street, technicals can help top traders make consistently profitable trades and can aid fundamental investors in better entry and exit points.

Just so we're clear, the companies I'm talking about today are hardly junk.

By that, I mean they're not next up in line at bankruptcy court--and many of them have very strong businesses. But that's frankly irrelevant to what happens to their stocks; from a technical analysis standpoint, sellers are shoving around these toxic stocks right now. For that reason, fundamental investors need to decide how long they're willing to take the pain if they want to hold onto these firms in the weeks and months ahead. And for investors looking to buy one of these positions, it makes sense to wait for more favorable technical conditions (and a lower share price) before piling in.

So, without further ado, let's take a look at four "toxic stocks" to sell--and when to sell them.

Canadian Natural Resources Ltd.

First on the list of potentially toxic trades is Canadian Natural Resources Ltd. (CNQ - Get Report) . CNQ is a $34 billion oil and gas producer that's been a notable laggard in the past few months--since peaking back in December, shares have shed 13.5% of their market value, tumbling twice as badly as the rest of the energy sector while the S&P rallied.

The bad news is that CNQ could have further to fall this March, despite rallying almost 5% on positive earnings yesterday ...

CNQ is forming a descending triangle pattern, a bearish continuation setup that's formed by horizontal support down below shares at $28.50, and downtrending resistance to the top-side. Basically, as this stock has pinballed in between those two technically significant price levels, shares have been getting squeezed towards a breakdown. If $28.50 gets violated, we've got a sell signal in this stock. Unfortunately, yesterday's earnings beat doesn't change CNQ's technical trajectory; it only brings shares back up to resistance for a third time since February.

CNQ has an extra red flag showing up in the form of relative strength, the indicator down at the bottom of the price chart. Relative strength has been making lower highs in shares since this stock's winter price highs, indicating that shares are still meaningfully underperforming in 2017. Keep a close eye on $28.50 in the next couple of weeks.

Magellan Midstream Partners LP

Another energy-related stock that's making our list of potentially bearish chart setups is $18 billion midstream operator Magellan Midstream Partners LP (MMP - Get Report) . The big difference here is that Magellan has actually been a strong performer since November, up almost 20% since the middle of that month. But it might be time for MMP shareholders to think about taking some gains off the table here ...

Magellan spent the past month and change forming a double top pattern, a bearish price setup that looks just like it sounds. The double top is formed by a pair of swing highs that peak at approximately the same price level, separated by a low that marks the line in the sand that triggers downside risk ahead. For Magellan, the price level to watch is $78 support, a level that got violated last week. Shares are consolidating just below the breakdown level, which isn't uncommon, but the downside risk is open at this point.

MMP's bearish setup is short-term, but it's worth waiting if you're thinking about being a buyer soon ...

Price momentum, measured by 14-day RSI in Magellan's chart above, is an extra red flag to pay attention to in this price setup. That's because our momentum gauge rolled over in January, making lower highs on the pair of peaks that make up the double top pattern. Momentum is a leading indicator to price, and the lower peaks create bearish confirmation that suggests buying pressure is waning here. Wait for MMP to establish some higher lows again before you think about going long.

Starbucks Corp.

Things are looking pretty straightforward right now in shares of coffee chain Starbucks Corp. (SBUX - Get Report) --unfortunately.

Starbucks has been pointing lower in a downtrending channel since December, showing traders a technical price pattern that's about as simple as they get. Starbucks' downtrend is formed by a pair of parallel trend lines that have corralled most of this stock's upside on every attempt to break higher. While trendline support down at the bottom of the channel (at S1) has been a bit more permeable than trendline resistance, it's the price ceiling at resistance that we're more concerned with here.

Last week's bounce off of resistance is our sell signal. Waiting for that bounce lower before clicking "sell" is a critical part of risk management for two big reasons: it's the spot where prices are the highest within the channel, and alternatively it's the spot where you'll get the first indication that the downtrend is ending. Remember, all trend lines do eventually break, but by actually waiting for the bounce to happen first, you're confirming that sellers are still in control before you unload shares of Starbucks.

Sasol Ltd.

Last on our list of potentially toxic trades is chemicals and energy stock Sasol Ltd. (SSL) . Sasol is another stock that's starting to look "toppy" after a pretty strong run from November's lows. Now, shares are sitting just above a classic breakdown setup as we head further into March trading.

The price setup playing on in shares of Sasol is a head and shoulders top, a bearish reversal pattern that indicates exhaustion among buyers. The pattern is identified by two swing highs that top out at approximately the same level (the shoulders), separated by a higher high (the head). The sell signal triggers when Sasol's neckline gets materially violated--that happens at the $28 price level.

If and when the breakdown in Sasol happens, prior support at $25 becomes a logical downside target based on prior support at that level back in July, September, and November. In short, you don't want to own it while shares sniff out their next price floor this spring ...

At the time of publication, author had no positions in the stocks mentioned.