Sucre is regarded as a strong defensive catcher, but has hit just .067 (1-for-15) in six games this season for Seattle and .186 in 35 career games.
Ruggiano, 33, hit .214 with four doubles, two home runs and three RBIs in 36 games after being acquired from the Cubs over the offseason for left-hander Matt Brazis.
Ruggiano was already limited in his playing time by the frequent use of Nelson Cruz in right field, so the acquisition of Mark Trumbo in the deal with Arizona figured to further reduce his role.
"Those things are never easy," manager Lloyd McClendon said. "It was a very difficult decision, but you've got to have a backup catcher and you can only carry 25, so somebody had to go. Obviously there was going to be a tremendous lack of playing time for whoever that guy was. Hopefully this gives him the opportunity to catch on with somebody else."
Ruggiano has hit .255 with 45 home runs and 140 RBIs in 434 career games over parts of seven seasons with the Rays, Marlins, Cubs and Mariners.
• Mariners right-hander Hisashi Iwakuma threw 27 pitches -- all fastballs -- Thursday in his first bullpen session since straining his right lat muscle and going on the 15-day disabled list in late April.
"I felt good, no stress or tension. I was pain free," Iwakuma said through translator Antony Suzuki. "It was a good bullpen."
Iwakuma will throw off the bullpen mound again Sunday, then accompany the team on its upcoming road trip so he can continue throwing before going out on a Minor League rehab stint later this month.
Pitching coach Rick Waits was pleased with the 33-year-old's initial return to the mound.
"He was very good; better than I anticipated," Waits said. "I was pleasantly surprised. I anticipated he'd be good, but this was better than I thought it would be."
If all goes well, Iwakuma could potentially be ready to rejoin the Mariners before the All-Star break in mid-July.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.