Lopez, who was in Philadelphia on Wednesday for a physical, remains with the Astros on Thursday. The two teams were working on a deal to send Lopez to Philadelphia in exchange for a pair of Minor League prospects, but the Astros are exploring other options.
Astros general manager Jeff Luhnow isn't commenting on potential trades.
Lopez has been a workhorse member of the Astros' bullpen the past three years, going 6-3 with a 2.17 ERA last year in 64 games. He also had a career-high 10 saves after assuming the club's closer role following the trade of Brett Myers and ineffectiveness of Francisco Cordero.
He posted the lowest walks-per-innings ratio among all National League relievers (1.09) last season after setting the franchise record in 2010 by issuing only five walks in 67 innings. He began last season by facing 78 batters without issuing a walk.
Lopez is eligible for arbitration for the first time in his career and after making $515,000 will have to be tendered a contract by Friday. The Astros claimed him off waivers on April 10, 2009.