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.

Vanguard Capital Opportunity Inv (VHCOX) has a 0.4% expense ratio and 0.39% management fee. VHCOX 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. With yearly returns of 14.32% over the last five years, this fund clearly wins.

WCM Focused Intl Equity Investor (WLIVX): 1.1% expense ratio and 0.82% management fee. WLIVX is a Non US - Equity fund. Many of these funds like to allocate across emerging and developed markets, and will often focus on all cap levels. WLIVX, with annual returns of 10.22% over the last five years, is a well-diversified fund with a long track record of success.

Nuveen LargeCap Value I (TRLHX Quick QuoteTRLHX - Free Report) : 0.42% expense ratio and 0.39% management fee. TRLHX 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. With a five-year annual return of 12.47%, 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.