NEW YORK ( TheStreet) -- With shares of Abbott Laboratories ( ABT) down by more than 15% since May, investors in the healthcare conglomerate are still trying to figure out whether management was correct in its decision earlier this year to separate the company's strong drug business into a new spinoff entity called AbbVie ( ABBV).While the decision to break up the company was initially met with excitement, the remaining portions of Abbott, which consists of (among others) the devices and nutrition businesses, have struggled with revenue growth. Consequently, since the stock reached a 52-week high of $38.77 per share in May, shares have not only lagged both Johnson & Johnson ( JNJ) and Medtronic ( MDT), but Abbott has also been outperformed by its spun-off arm AbbVie. With the company due to report its third-quarter results on Wednesday, I believe the only way to justify buying this stock -- even on this recent pullback -- is for management to demonstrate not only better operating balance between the company's four remaining business segments, but for Abbott to show that it can compete more effectively against Johnson & Johnson in areas like medical devices. Abbott investors will point out that the company has been performing well in both diagnostics and nutrition. Though this might be true, the stock has been sliding because the devices business, which is the company's largest segment, continues to underperform, including posting flat results in the July quarter. By contrast, Johnson & Johnson grew its devices business by 12%. The other issue for Abbott is that, even when there's good news, it introduces some causes for concern. For instance, Abbott investors are correct to point out the meaningful improvements management has made in the nutrition business. But that has done little to advance margins, given that the company recently posted almost a 1% year-over-year decline. I won't deny that management deserves credit for the improvements in the nutrition business, which posted 8% revenue growth in the July quarter. But the fact that nutrition now accounts for more than 30% of the company's overall revenue demonstrates a lack of balance and is an exploitable weakness in the company's overall business.