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.

Virtus KAR Small-Cap Core I (PKSFX Quick QuotePKSFX - Free Report) : 0.99% expense ratio and 0.75% management fee. PKSFX is a Small Cap Blend mutual fund, allowing investors a way to diversify their funds among various types of small-cap stocks. With annual returns of 13.84% over the last five years, this fund is a winner.

Neuberger Berman Guardian Adviser (NBGUX Quick QuoteNBGUX - Free Report) . Expense ratio: 1.17%. Management fee: 0.88%. NBGUX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value. This fund has managed to produce a robust 11.51% over the last five years.

T. Rowe Price All-Cap Opportunities Fund (PRWAX Quick QuotePRWAX - Free Report) . Expense ratio: 0.81%. Management fee: 0.63%. Five year annual return: 14.33%. PRWAX 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.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.