Strange price moves may be apparent on the commodities markets this week as two of the world's most widely followed commodities indexes undertake their annual rebalancing, analysts said.

Macro-economic and geopolitical concerns continue to dominate these markets, but the movement of large sums of money as the Dow Jones-UBS Commodity Index and the Standard & Poor's GSCI shift the weighting of their positions could disrupt this pattern.

The indexes themselves don't buy or sell anything, but they are tracked by mutual funds, exchange-traded funds and other types of investors who base their trades on the indexes. Combined, those investments represent billions of dollars.

According to estimates from Morgan Stanley, metals, grains and soft commodities will each see over $1 billion in inflows as a result of this week's shift, while outflows of $660 million are expected from energy sub-indexes.

The rebalancing is mostly a matter of selling last year's outperformers and buying underperformers to bring the composition of the portfolio back in line, said Saxo Bank's senior commodity strategist Ole Hansen.

This year the index reweighting will mean that agriculture, livestock and industrials will be bought, while precious metals and energy will be sold, with the exception of natural gas and Brent crude.

"A lot of major trading desks are looking at this in some depth as there is a perception that there may be some profit opportunities stemming from this," said Nicholas Brooks, head of research and investment strategy at ETF Securities.

Most likely to be affected are the markets with the least liquidity to absorb the large movements of money--potentially having an upside price impact on sugar, nickel, cotton, wheat and zinc--though analysts said the changes may have already been priced in to a large degree.

"Anticipation of this rebalancing was a sizeable factor in gold's drop to a $1,522 a troy ounce low on Dec. 29," said UBS precious metals analyst Edel Tully.

Still, market watchers should stay tuned for some odd moves this week, especially as this year the rebalancing comes with an added twist.

The DJ-UBS index is set to add Brent crude to its portfolio for the first time, reducing its exposure to U.S. benchmark West Texas Intermediate, while the S&P-GSCI index will also adjust its weighting in favor of Brent.

"The Brent market is going to take more financial flows in 2012 so that should be positive for Brent," said Torbjorn Kjus, oil market analyst at DnB NOR.

"We're already seeing part of that impact because the Brent market is moving stronger than WTI," he added.

The premium Brent crude commands over WTI rose Monday to its highest level since mid-November, helped by escalating tensions between Iran and the West as well as the movement of investment flows.