Barclays became the first big Wall Street firm to upgrade a major oil stock in the wake of the crash in prices, a tentative sign that there may finally be some value in the energy patch following a slaughter in the sector's shares.

Barclays upgraded BP to "overweight" and called for the company to slash production and fire employees in order to get costs in line after oil's drop. The firm lowered its Brent crude oil estimate to $70 a barrel for 2015. That's about where it was trading Wednesday.