PHILADELPHIA — The Phillies clung to a one-run lead as Taijuan Walker, the newly minted one-inning reliever, trotted out of the bullpen to pitch the bottom of the sixth inning. Only, the right-hander didn’t know just how close the game was.

Walker, a converted starter who spoke candidly on Tuesday night about the adjustments his new role has required, didn’t check the score before he entered the game. He thought Philadelphia was leading by two runs, so it came as a surprise when he saw the two-run home run he gave up to Ian Happ put the Cubs ahead in an eventual 8-4 Chicago victory at Citizens Bank Park. It was a teaching moment in his bullpen crash course.

“I didn’t really look at the score until after,” Walker said. “Honestly, I thought we were up by two until I saw that they were up by one. But I don’t know. It’s just all new to me. Still trying to learn and adjust.”

A 13-year major leaguer, Walker has been moved out of the rotation and assigned to a short-burst relief job in an attempt to help a thin bullpen unit. It’s clearly not his preference, and Walker declined to go as far as to say he’s been enjoying the opportunity. But it’s what the team has asked him to do, and he’s willing to take the ball and do it.

“I’m accepting the challenge,” Walker said. “I’m gonna go out there, do the best I can and compete and do what’s needed, I guess. Kind of just go from there, take it day by day.”

Walker has now made three one-inning appearances as a reliever. After two scoreless outings, he surrendered two runs and took the loss on Tuesday. His lone four-seam fastball hit 93.6 mph, and he threw an 88.9 mph cutter in off the plate to Happ, who hit it 361 feet to right field for his second homer of the game. Beforehand, Walker had nearly escaped the inning with a double play, but the turn wasn’t quick enough to save him from the damage.

“I think the stuff ticked up a little bit from the other day,” Phillies manager Rob Thomson said. “… I thought it was OK.”

The whole situation is a work in progress.

“I’m getting more used to it, I guess,” Walker said. “I thought today, arm wise and stuff wise, I felt pretty good, but I’m still trying to get used to it and just the whole routine. But I thought today was better than the previous times out. Obviously, the home run sucks, but I thought, stuff wise, it was better.”

In his old days as a starter, Walker could brush off a homer and move on to the next inning. Not so much anymore.

“It’s new to me, so it’s frustrating,” he said.

At 32, Walker has been learning on the fly about how to warm up quickly, pitch more often and stay ready both physically and mentally. He’s asked teammates like Joe Ross and Matt Strahm for advice. It hasn’t been easy.

“Honestly, I’m used to playing catch once a day and kind of calling it a day, instead of playing catch, sitting down for a couple hours, getting hot and warmed up again and then going to sit for a couple hours in the bullpen and getting ready again,” Walker said. “That’s something new.”

He’s also still searching for the right routine out there in the bullpen. Walker said he was “pretty sore” after pitching twice in three days in his previous two appearances, so he’s not sure when he’d be able to go on back-to-back days.

At this point in his career, maybe there is no perfect formula for Walker to have success as a reliever. He’d been a starter for this long and has an arsenal that wouldn’t typically be utilized out of the bullpen. But maybe he can figure out a way to get batters out and provide some assistance in the middle and late innings. With rookie starter Mick Abel on the roster to contribute in Aaron Nola’s absence, the Phillies can let Walker stick it out and see what they have.

In any case, it’s clear that he has quite a few adjustments to make before he can be seen as a trusted bullpen arm.