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 best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

AMG Yacktman I (YACKX Quick QuoteYACKX - Free Report) : 0.7% expense ratio and 0.43% management fee. YACKX is an All Cap Value mutual fund, which invests in small, medium, and large-cap companies, though they end up focusing on bigger firms due to percentage of assets. YACKX has achieved five-year annual returns of an astounding 11.7%.

Thrivent Small Cap Stock S (TSCSX Quick QuoteTSCSX - Free Report) : 0.81% expense ratio and 0.63% management fee. TSCSX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. With yearly returns of 12.18% over the last five years, TSCSX is an effectively diversified fund with a long reputation of solidly positive performance.

Fidelity Puritan Fund K (FPUKX Quick QuoteFPUKX - Free Report) : 0.42% expense ratio and 0.38% management fee. FPUKX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. With a five-year annual return of 11.61%, this fund is a well-diversified fund with a long track record of success.

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.