Last week, U.S. crude rose more than 8 percent and international benchmark Brent finished up 4.6 percent.
The advances came after Saudi Arabia scuttled a proposed deal among oil producers to freeze production at January levels. The kingdom insisted Iran participate, but Tehran had long said it would not turn off the taps until its output returned to presanctions levels.
Croft said top oil producer Russia cannot add much more output, and Iran is likely just 100,000 to 150,000 barrels from its goal, after adding about 400,000 already.
"Everybody in this market is pretty much capped out, so when they say they're going to bring it on, there's not much more to bring on at this point," she said.
To be sure, Neil Atkinson, head of the oil industry and markets division at the International Energy Agency, told CNBC last week he believes Saudi Arabia and Russia will continue to "pump as much oil as possible."