Lopez has been a workhorse member of the Astros' bullpen the past three years, going 6-3 with a 2.17 ERA in 64 games in 2012. 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.
Lopez posted the lowest walks-per-nine-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 pitched. He began last season by facing 78 batters without issuing a walk.
Astros general manager Jeff Luhnow did not confirm the discussions.
The departure of Lopez would leave the Astros with a hole at closer, something the team will likely address in the near future.
The Astros claimed Lopez off waivers on April 10, 2009.