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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

AQR Small Cap Multi-Style I (QSMLX Quick QuoteQSMLX - Free Report) : 0.6% expense ratio and 0.45% management fee. QSMLX is a Small Cap Blend mutual fund that usually targets companies with a market capitalization of less than $2 billion. QSMLX has achieved five-year annual returns of an astounding 9.17%.

Vanguard Windsor-II Investor (VWNFX Quick QuoteVWNFX - Free Report) : 0.34% expense ratio and 0.33% management fee. VWNFX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. VWNFX, with annual returns of 12.42% over the last five years, is a well-diversified fund with a long track record of success.

Victory RS Global Growth A (RSGGX Quick QuoteRSGGX - Free Report) . Expense ratio: 0.85%. Management fee: 0.6%. Five year annual return: 11.44%. RSGGX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations.

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.