Monday was Labor Day and, no surprise, the Mariners continued to work on their roster.
While Hannemann is expected to join the big-league club prior to Tuesday's game against the Astros, Frankoff is not — at least at this point.
The Mariners cleared space on their 40-man roster for the additions by placing reliever David Phelps on the 60-day disabled list because of an impingement in his elbow and by designating reliever Zac Curtis for assignment.
Hannemann, 26, is a left-handed hitter who batted .240 this season while splitting 113 games at Triple-A Iowa (79) and Double-A Tennessee. He also stole 29 bases in 35 attempts.
"He’s a center fielder," manager Scott Servais said. "A pretty athletic guy. He can run and defend."
Frankoff, 29, is an eight-year professional who made his major-league debut earlier this year for the Cubs but spend most of the season at Iowa, where he was 2-8 with a 4.71 ERA in 24 games, including 21 starts.
Acquiring Hannemann appears to reflect concern over Jarrod Dyson’s renewed groin injury. Dyson played just two games after returning from an 11-game absence before the problem returned Saturday while running to first base.
"We’ll see how Jarrod is doing," Servais said. "I think he’s going to be back and be OK. It’s something he’s going to have to manage for the rest of the season."
The move to claim Hannemann, ironically, came just four days after the Mariners traded outfielder Leonys Martin to Cubs for a player to be named later or cash considerations.
At the time, Dyson’s anticipated return from the disabled list left no room for Martin on the roster.
Hannemann was a third-round pick by the Cubs in 2013 and has a .247/.312/.381 slash (batting average/on-base percentage/slugging percentage) in five minor-league seasons. He has never played in the big leagues.
Frankoff was a 27th-round pick by Oakland in 2010. He is 27-33 with a 3.80 ERA in 280 minor-league games, including 70 starts, over eight seasons.
Phelps, 30, returned to the disabled list Sept. 1 because of renewed elbow problems. He missed 14 games in August because of the same injury and could be headed for cleanup surgery.
"Phelpsie is going to be shut down," Servais confirmed. "That's the smart thing to do now before it turns into something bigger."
Curtis, 25, appeared in three big-league games this season but spent most of the year at Double-A Arkansas, where he was 1-2 with a 3.51 ERA in 41 appearances.
Bob Dutton: @TNT_Mariners