Fuentes did not share specifics of the circumstances with the Cardinals, but those who talked with him on Monday were led to believe that Fuentes does not expect to pitch again this season. If that's the case, that would put a wrap on his Cardinals tenure only six appearances after it began.
"He called me and explained that he needed to go home to get this resolved," Matheny said. "I told him I completely understood."
When it was clear that Fuentes would not be reporting to Busch Stadium for Tuesday's series opener against the D-backs, the Cardinals moved Fuentes to the restricted list. That removes him from both the 40- and 25-man rosters, and it allowed St. Louis the flexibility to recall pitcher Trevor Rosenthal from Triple-A.
Fuentes will not collect a paycheck from the Cardinals during his absence. He will remain on the restricted list until the end of the season, at which time his contract runs out and he becomes a free agent.
Fuentes' departure leaves the Cardinals with two left-handers in the bullpen. And the timing of the move -- the non-waiver Trade Deadline has already passed -- makes it unlikely that the Cardinals can upgrade by adding another reliever to replace the veteran presence Fuentes offered.
"If you think back to our trading Deadline strategy, he played into how we made decisions," Mozeliak said. "To have it end this way is definitely disappointing. It's disappointing because we were looking for that veteran leadership out of the bullpen. We thought he could do some quality things from the left side. By not having that, that's definitely a negative."
Signed to a Minor League contract in mid-July, Fuentes joined the big league team on July 25 and allowed five earned runs on six hits and five walks in the five innings he pitched. Fuentes had started the year with the A's, but became a free agent after being released in early July.
The timing of Oakland's roster move seemed ideal for the Cardinals, who were already searching for left-handed relief by the time Fuentes became available. Now, the club is left to depend on Marc Rzepczynski and rookie Barret Browning for the foreseeable future.
"I think having two is something that we're going to deal with just fine," Matheny said. "If the starters are doing their job, then most of this stuff falls into place. That's what we're just going to hope [going] forward."
If the Cardinals want to add another left-hander to the 'pen when rosters expand in September, Triple-A reliever Sam Freeman would be the most likely candidate to be called up. He is already on the club's 40-man roster.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.