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Big-name fund managers, in finance speak, will either be redeployed, exploring new opportunities or spending more time with their families after shake-ups on the cusp of a bull market.

Fund-manager appointments are highly coveted in the investment world, but are also fairly fickle. The real reason for some departures can be unclear. Regardless of the circumstances, here are recent changes to the largest and most well-known funds.

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Fidelity Mega Cap Fund

(FGRTX) - Get Report

.

Fidelity

is notorious for musical chairs in its fund-management suite, presumably to keep things from stagnating. Richard Mace is the latest manager to leave his post. His departure is because of retirement rather than reassignment, according to Fidelity. Matthew Fruhan will succeed him at the helm of the Mega Cap Fund.

The $315 million mutual fund invests in

Exxon Mobil

(XOM) - Get Report

,

Microsoft

(MSFT) - Get Report

,

ConocoPhillips

(COP) - Get Report

and

JPMorgan

(JPM) - Get Report

. Over the past year, Fidelity Mega Cap has barely outperformed its benchmark, the

S&P 500

index, by 27 basis points.

Janus Global Opportunities Fund

(JGVAX) - Get Report

.

The terms of Jason Yee's departure from

Janus

are more murky. Janus's press release says he would be leaving to pursue other interests, but some rumblings online seem to suggest this was a long time coming. Still, the $84 million Global Opportunities Fund outperformed its benchmark, the MSCI World Index, over the past year by nearly 11 percentage points.

The main source of displeasure with Yee comes from trailing his peer group as well as several years of losses.

The Global Opportunities Fund has large stakes in

News Corp.

(NWSA) - Get Report

,

Dell

(DELL) - Get Report

and

UnitedHealth Group

(UNH) - Get Report

, among others.

Yee has been replaced by Gregory Kolb, an executive vice president at Janus and a CFA charterholder.

Janus Worldwide Fund

(JAWWX) - Get Report

.

The Worldwide Fund also was under Yee's direction. Over the past year, it didn't fare as well as the Global Opportunities Fund. With a one-year decline of 37%, it underperformed the MSCI World Index by 27 basis points.

Yee's post was taken over by Laurent Saltiel, a Harvard MBA and a CFA charterholder.

Major holdings for the $1.85 billion fund include

eBay

(EBAY) - Get Report

, Dell,

Yahoo!

(YHOO)

and UnitedHealth Group.

AllianceBernstein Small/Mid Cap Growth Fund

(CHCLX) - Get Report

.

The Small/Mid Cap Growth Fund at AllianceBernstein takes more of a team approach. Five people on the nine-member team were recently removed from the management roster. The job losses were tied to planned staffing cuts designed to lower costs at the wobbling management shop.

Lackluster performance may have sealed the fate of these managers as the $341 million fund underperformed the Russell Mid Cap Growth Index by 42 basis points.

Performance relative to a benchmark is usually the metric fund managers tout when trying to attract new customers. However, relative performance is a far more meaningful statistic. With some management fees well over 1%, outperformance needs to be substantial to justify investment in an actively managed fund versus a low-cost index fund. Performance slightly above a benchmark isn't worth the costs associated with investing in a traditional mutual fund. As a result, fund managers sometimes find themselves with much more time for their families.

Prior to joining TheStreet.com Ratings, David MacDougall was an analyst at Cambridge Associates, an investment consulting firm, where he worked with private equity and venture capital funds. He graduated cum laude from Northeastern University with a bachelor's degree in finance and is a Level II CFA candidate.