Shurmur, who said "we'll see" about the Giants' QB situation heading into their Week 9 bye, explained he had a discussion with Manning about his need to play better, per ESPN.com. The coach also noted backup Kyle Lauletta faced "internal consequences" after being arrested last week, but won't be suspended.
The Giants head into the second half of the season with a 1-7 record and the 27th-ranked scoring offense in the NFL at 18.8 points per game.
Manning, who was benched for one game last year because of consistently lackluster play, has failed to showcase sustained improvement in 2018.
The 37-year-old Ole Miss product has completed a career-best 68.3 percent of his throws, but he's parlayed that into just eight touchdowns with six interceptions across eight appearances.
Shurmur wouldn't commit to keeping him as the starter for the rest of 2018 amid the struggles.
"Let's get on a run here so there's no decisions to be made," he told reporters.
Meanwhile, Lauletta apologized for his arrest last week and noted Manning has been there for him throughout the situation.
"Eli Manning is one of the best teammates I've ever had," he said. "He was there for me and he was supportive...he reached out later that day and it meant the world to me."
The 2018 fourth-round pick would be first in line to assume the reins of the Giants' offense if the coaching staff decides to bench its veteran starter. Alex Tanney is the other quarterback on the roster.
Manning has one season left on his four-year, $84 million contract, but with a $23.2 million cap hit in 2019 and just $6.2 million in dead cap if he's released, New York may decide to let him go in the offseason.