Jan 5 (Reuters) - The Organization of the Petroleum Exporting Countries (OPEC) will likely take steps to boost oil prices, which started the year in free-fall, the chief executive of top shale producer Pioneer Natural Resources Scott Sheffield said on Thursday.

"Saudi is not going to let Brent stay around $75 a barrel," he told investors at a Goldman Sachs conference in Miami, Florida. "It wouldn't surprise me if they had another cut."

His comments came as oil posted its biggest two-day loss to start the year in three decades this week. Brent futures were trading around $78 a barrel on Thursday morning. (Reporting by Liz Hampton in Denver; Editing by Jan Harvey)