Rodri – who became the Premier League champions’ record signing when he joined for £63million from Atletico Madrid in July – was deployed at centre-back alongside Fernandinho for the second time in the space of a week on Tuesday, with John Stones again left on the bench.
But, in getting back to challenge Alejandro Gomez, Rodri instantly signalled to the bench that he needed attention.
Guardiola confirmed after the match that Rodri had picked up a hamstring injury, but said the severity is as yet unclear.
“Tomorrow [Wednesday] we will know,” Guardiola said. “Hopefully [Rodri will be out] between 10 days if it is not broken [torn].
“If it is broken, it will be three weeks or one month.
“It is hamstring, it looks like. When a guy runs and puts his hand in the hamstring position, it is a hamstring.”
Stones – who bore the brunt of frustration from Pep as he wasn’t ready to replace Rodri from the bench – came on to provide a more conventional centre-back option.
“It’s the first season for Rodri, he’s slotted in brilliantly in a new league, a different for him and he’s breezed it,” the England international told BT Sport.
“Credit to Fernandinho, he’s helped him along. We work on playing different positions in training all the time, knowing everyone’s jobs and the roles on the pitch, so you can almost play blind when you have the ball.
“It’s been good to be back out on the pitch for me on a personal note, [but I’m] upset to see Rodri has a little injury. We’ll see how it is.”
Before kick-off, City announced they were waiting to discover how serious a knee injury suffered by left-back Oleksandr Zinchenko might prove to be.
Winger Leroy Sane, meanwhile, is continuing his rehabilitation from cruciate ligament damage sustained during August’s Community Shield clash with Liverpool.