The Cubs signed Japanese closer Kyuji Fujikawa to help solidify the back end of the bullpen, but the 32-year-old righty has struggled to stay on the field.
Fujikawa exited Sunday's game in Cincinnati with a forearm injury and was placed on the 15-day disabled list Monday. He is scheduled for an MRI Tuesday morning.
"We don't know [the issue] yet," general manager Jed Hoyer said before Game 1 of the Crosstown Cup at U.S. Cellular Field Monday. "We'll have a better feel for it tomorrow. We're cautiously optimistic that it will be the same thing he had before. That's certainly our hope."
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Fujikawa, who saved more than 200 games in Japan, spent almost a month on the disabled list earlier this season with a forearm strain. He felt something during the sequence to Reds first baseman Joey Votto in the ninth inning Sunday and was seen shaking his hand on the mound.
After a rough start to the season, Fujikawa had turned things around since he returned from the DL May 10. In his last 7 2/3 innings, he had allowed just three hits, one walk and one run, while striking out 10. Unfortunately, the lone run was a big one -- a game-winning homer to Mets second baseman Daniel Murphy May 19.
"He was actually throwing really well," Hoyer said. "He gave up the one home run, otherwise the walk:strikeout ratio was really good. We were starting to see the fastball that made him really successful in Japan.
"I felt like he was getting comfortable with his role here. We're all frustrated that it's happened twice. We're still excited to have him on our club and hope he can come back and build on what he's started."
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If it is the same forearm injury, Hoyer indicated the Cubs would exercise more caution and allow Fujikawa more time to recover fully from this latest setback.
The Cubs replaced Fujikawa on the 25-man roster with right-hander Alex Burnett, whom they claimed on waivers Monday afternoon from the Baltimore Orioles.
"Alex had a solid season last year," Hoyer said. "He's a guy we liked and talked about acquiring a couple other times. Given Fuji's injury, we felt it was the right thing to do at the right time. The timing worked out well with the waiver wire."
Burnett, 25, has made 176 big-league appearances over his four-year career and turned in a solid season with the Twins last year, going 4-4 with a 3.52 ERA, 1.35 WHIP and 10 holds. He pitched in just two games with the Orioles this season before he was placed on waivers.