There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

Davenport Small Cap Focus Fund (DSCPX Quick QuoteDSCPX - Free Report) has a 0.89% expense ratio and 0.75% management fee. DSCPX is a Small Cap Blend mutual fund that usually targets companies with a market capitalization of less than $2 billion. With yearly returns of 10.57% over the last five years, this fund clearly wins.

JPMorgan Disciplined Equity I (JDESX Quick QuoteJDESX - Free Report) . Expense ratio: 0.35%. Management fee: 0.25%. JDESX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. This fund has managed to produce a robust 10.85% over the last five years.

MFS Mass Investors Growth Stock I (MGTIX Quick QuoteMGTIX - Free Report) . Expense ratio: 0.46%. Management fee: 0.33%. Five year annual return: 11.54%. MGTIX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.