CSL Ltd (ASX: CSL) has long been regarded as one of the highest-quality companies on the ASX, but its recent share price performance has been anything but inspiring.

The global biotechnology giant is currently trading at $247.88, not far off its five-year low of approximately $233.00.

The key question for investors is whether this is a rare buying opportunity or a sign of further weakness ahead.

A tough few years for CSL shares

CSL has faced several headwinds in recent years, leading to a slower-than-expected recovery in its margins.

The COVID-19 pandemic severely disrupted its plasma collection operations, impacting the supply of a critical raw material for its core immunoglobulin (IG) therapies. While collection volumes have rebounded, cost pressures remained for some time and delayed a return to pre-pandemic profitability.

In addition, the company has faced challenges in integrating its $16 billion blockbuster acquisition of Vifor Pharma, which expanded its footprint into nephrology and iron deficiency therapies.

These factors have weighed on sentiment and contributed to a significant de-rating in CSL's valuation.

At a 12-month forward price-to-earnings (P/E) ratio of around 23x, CSL is trading well below its 10-year average of 31x, suggesting that investors are pricing in a prolonged period of slower growth.

However, a number of analysts disagree with the latter and believe strong and sustainable growth has now arrived.

A buying opportunity for patient investors?

Bell Potter remains very bullish on CSL and its shares. It has a buy rating and a $335.00 price target on them, implying 35% upside from current levels.

The broker highlights CSL's track record of deploying capital effectively and generating high returns, as well as the strong medical need for its plasma-derived therapies. With margins expected to recover, it sees CSL delivering above-market earnings growth over the next few years. It said:

CSL presents an attractive buying opportunity as we anticipate the start of a margin recovery phase for CSL, driving above-market earnings growth over the next few years.

Over at Goldman Sachs, its analysts are also feeling very bullish. The broker has a buy rating and $318.40 price target on its shares.

It notes that CSL is a global leader in immunoglobulins, a market that continues to experience strong demand. It also sees CSL gaining market share in haemophilia, hereditary angioedema (HAE), and influenza vaccines.

Importantly, Goldman believes the company's operational improvements should drive margin expansion, making the current valuation look significantly cheap. It said:

We believe CSL's valuation multiple de-rate is onerous considering the growth outlook, particularly for IG therapies.

Foolish takeaway

CSL's share price decline has been frustrating for investors, but history suggests that patience is often rewarded with high-quality businesses.

While the past few years have been disappointing, the company remains a dominant player in its industry, and its long-term growth outlook remains intact.

So, with its shares down in the dumps, now could be a great time to make an investment.