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

MFS Growth Fund A (MFEGX Quick QuoteMFEGX - Free Report) : 0.84% expense ratio and 0.49% management fee. MFEGX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. MFEGX has achieved five-year annual returns of an astounding 15.6%.

VY T. Rowe Price Diversified Mid Cap Growth Investor (IAXIX Quick QuoteIAXIX - Free Report) : 0.78% expense ratio and 0.74% management fee. IAXIX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. With yearly returns of 11.74% over the last five years, IAXIX is an effectively diversified fund with a long reputation of solidly positive performance.

Emerald Growth Fund Institutional (FGROX Quick QuoteFGROX - Free Report) is an attractive large-cap allocation. FGROX is a Small Cap Growth mutual fund building their portfolio around stocks with market caps under $2 billion and large growth opportunities. FGROX has an expense ratio of 0.79%, management fee of 0.62%, and annual returns of 7.46% over the past five years.

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.