CHICAGO -- For a few fleeting innings, it felt like the Red Sox were going to have a sparkling return to Wrigley Field in their first trip to the friendly confines in a decade.

But as Friday afternoon wore on, the mood of the Red Sox resembled the clouds they played under all day.

Not only did leads of 4-0 and 5-3 disappear in a 6-5 loss, but another starting pitcher (Rich Hill) suffered an injury that could require a stint on the injured list, and reliever Hansel Robles had the latest in a recent stream of tough outings.

Here is a closer look at the unraveling of the day.

Hill: "I feel stupid for staying in"
Facing the team he made his first 57 career starts for, Hill’s return to Wrigley was grand for the first four innings. In fact, the 42-year-old took a one-hit shutout into the fifth.

But it was in the fifth when Boston’s Friday started to turn dark.

The 42-year-old wound up spraining his left knee on the first pitch of his at-bat against Willson Contreras with one out in the fifth. Catcher Christian Vázquez could see something was amiss. So after Contreras walked, Vázquez signaled for manager Alex Cora and the training staff.

Hill tried to tough it out, but gave up a single to Ian Happ and hit Patrick Wisdom. At that point, Cora took him out.

“I just felt a pop in my knee. I feel stupid for staying in, to be honest with you,” said Hill. “Stubborn. I put us in a really bad position. Unfortunately that falls on me. The stubbornness of staying in and wanting to compete and not coming out. I thought it was going to be just kind of a little tweak or whatever and pitch through it. But we’ll find out what the extent of what’s going on in the next couple of days.”

In 2019, Hill suffered a left knee sprain that kept him off the Dodgers’ roster for a month.

“I’ve had some MCL issues before, in 2019,” said Hill. “But I thought this might be something breaking up or some scar tissue or something like that. In the heat of the moment, being out there and competing, it was something that I thought I could pitch through.”

A few batters too late, it became apparent that wasn’t the case. Of late, Boston’s depth in the rotation has been tested. Garrett Whitlock and Nathan Eovaldi have been on the injured list since the second week of June. While they are both on the mend, it’s uncertain when they will return. Ace Chris Sale, who hasn’t pitched this season, might need just one more rehab start before returning to action.

The Red Sox should have a better idea of Hill’s timetable by Saturday.

“We’ll have to diagnose it and find out exactly what the extent of it is. Hopefully it’s not too serious,” said Hill. “It’s never something where you come out of a game where it’s a good thing. Just hoping for the best. Either way, I’ve been through a lot in this game, and I know I can recover from whatever it is and be back at some point.”

Robles in a rut
In his first eight appearances of the season, Robles didn’t allow a run. The veteran righty has fallen precipitously since then, posting a 9.20 ERA in 17 outings since April 29.

On Friday, entrusted with a 5-3 lead in the sixth inning, he suffered his sixth blown save in eight opportunities this season. The righty gave up two hits, three walks and three runs, taking the loss.

Robles declined comment after the tough outing.

“The slider is not good,” said Cora. “It’s kind of like a short cutter. There’s no sweeping action.”

While the Red Sox have Tanner Houck and John Schreiber as a dominant righty duo in the late innings, Cora is lacking dependable righties in the middle of the game.

“People have to step up,” Cora said.

When he is right, Robles has the arsenal to be one of those people. He’s just not executing.

“I mean, we’re talking to him. Right now, as far as the pitches and characteristics, the fastball is good, you see the velo today. It was actually really, really good, but the slider is not there,” said Cora. “The changeup is harder. We’ve got to keep working and get the secondary pitches a little bit better, and hopefully that can help.”