CINCINNATI — A Cubs pitching staff strained by injuries, a doubleheader and childbirth showed another crack when Pedro Strop blew a big lead in the seventh inning of an 8-6 loss Sunday to the Reds.
The defeat finished off a four-game sweep at the hands of the last-place Reds and sent the Cubs to Los Angeles, where it doesn’t figure to get any easier in a four-game series against the Dodgers.
Right-hander Tyler Chatwood’s departure early Sunday to be with his wife for the birth of their first child opened a starting spot the Cubs will fill Monday with right-hander Duane Underwood, who will make his major-league debut.
The Cubs already used a fill-in starter, right-hander Luke Farrell, on Saturday because of a schedule squeeze caused by a rainout-created doubleheader Tuesday. They got only 2 2/3 innings out of him.
One of the relievers used Saturday, left-hander Rob Zastryzny, left with tightness in his back that landed him on the disabled list.
And after watching Strop give up a three-run home run on his first pitch and a bases-loaded walk on his last during the Reds’ seven-run seventh, it’s hard to know whom to trust in a bullpen still missing setup man Carl Edwards Jr. (shoulder) and closer Brandon Morrow (back).
‘‘Stropy’s had plenty of rest, maybe too much rest,’’ manager Joe Maddon said. ‘‘I just really felt he was the right guy in that spot. It just didn’t work.’’
Strop had last pitched in the first game of the doubleheader Tuesday, throwing two scoreless innings.
‘‘It’s always good to be fresh; I’m not going to blame it on that,’’ Strop said. ‘‘It wasn’t there today. I didn’t have any command on my fastball, so I was going to my secondary pitches.
‘‘That’s a really tough one to swallow.’’
It spoiled an otherwise good start for Mike Montgomery, who allowed one run in six innings before the first three reached against him in the seventh, setting the stage for Strop.
And that came just one after reliever Brian Duensing took the brunt of a six-run Reds third.
“Of course it’s difficult,” Maddon said. “But when you’re missing a Carl Edwards and Morrow at the back end, there’s definition in that also. But no excuse.”
“Obviously, you’re talking about two of our best guys back there,” Strop said. “But we still have guys in there that can do the job.”
Yu know the answer?
Reinforcements might be on the way quickly.
Chatwood is expected to rejoin the rotation when the Cubs return home Friday to face the Twins, and $126 million right-hander Yu Darvish might be close to a return from the DL right behind that.
Darvish headed out Sunday to South Bend, Indiana, where he is scheduled to make a rehab start with the Cubs’ Class A affiliate. The Cubs are hoping for five or six innings and 60 to 75 pitches, Maddon said.
Darvish said he will need only one start before being activated, but Maddon said, ‘‘We’ll play it by ear.’’
Farrell was optioned to Class AAA Iowa after his start Saturday. Relievers Cory Mazzoni and Justin Hancock were recalled to fill his and Zastryzny’s roster spots.