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.

MainStay MAP Fund I (MUBFX Quick QuoteMUBFX - Free Report) : 0.7% expense ratio and 0.66% management fee. MUBFX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With annual returns of 12.84% over the last five years, this fund is a winner.

American Funds Washington Mutual Investors R3 (RWMCX Quick QuoteRWMCX - Free Report) is a stand out amongst its peers. RWMCX 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. With five-year annualized performance of 10.69%, expense ratio of 0.91% and management fee of 0.22%, this diversified fund is an attractive buy with a strong history of performance.

Rydex Nova H (RYNHX Quick QuoteRYNHX - Free Report) is an attractive large-cap allocation. RYNHX 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. RYNHX has an expense ratio of 1.48%, management fee of 0.75%, and annual returns of 14.52% over the past five years.

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.