This could knock the wind out of the market

One of the biggest buyers of stocks is taking a break.

U.S. corporations, which were the biggest buyers of stocks in the first quarter of 2014, have cut their announced buybacks to the lowest level in seven quarters, according to data compiled by TrimTabs Investment Research.

With companies not buying as much of their own stocks as they did before, could the wind be taken out of the market's sails just as it hits all-time highs?

"I am certainly worried about it," said Steve Cortes, founder of Veracruz TJM. Low interest rates due in large part to the Federal Reserve's bond-buying stimulus helped companies improve their balance sheets, argues Cortes. But, rather than making capital investments, concerns about the economy led companies to use their money to buy stocks.

(Watch: US stocks finish higher; S&P 500 near record close)

Buybacks have been one of the big drivers of earnings growth which, in turn, has helped to justify higher stock prices. But, with fewer buybacks, traders fear there may not be enough buyers to pick up the slack.

"I'm not so sure that mom and pop investors are ready to step up and replace those companies as the next buyer of stocks," Cortes said.

Richard Ross, global technical strategist at Auerbach Grayson, sees the benchmark S&P 500 index as vulnerable based on its technicals.

One the one hand, the short-term chart shows the index staying above its 150-day moving average. "We have been above that key longer term moving average since 2012," notes Ross, a "Talking Numbers" contributor. "In fact, I went back and looked at the entire 1990's bull run and you cannot find a period of time as long as the current period of time that we have remained above that entire 150-day."

(Read: The rich get richer as stock buybacks surge)

On the other hand, the longer-term chart gives Ross reason to worry. He sees the S&P 500 as having moved too far above its 50-week and 150-week moving averages, which he believes opens it up to as much as a 10 percent correction.

"The one thing that stands out for me is not so much the buying pressure, which is not particularly strong, but more so the absence of any selling pressure," Ross said. "It's not as if we are lurching higher as we did in the '90s with these fantastic explosions and stock prices to the upside. It's more so that no one is selling shares. The volatility has been muted."

That could signal an overbought market but such a situation could last for some time, said Ross. "No bell rings at the top," Ross added. "But, I do think we remain vulnerable by virtue of the fact we have been so far above trend it's almost an unprecedented rise."

To see the full discussion on the S&P 500, with Cortes on the fundamentals and Ross on the technicals, watch the above video.

Follow us on Twitter: @CNBCNumbers
Like us on Facebook: