The youngster was found after emergency services were called to Belle Vale Road at around 9pm on Tuesday, Merseyside Police said.
The alleged victim was left in a serious but stable condition after suffering a number of stab wounds during an incident on Fairbridge Road, Islington on Sunday.
They killed 28-year-old Abdul Samad for his iPhone and little more than "aggression and blood lust" as they swept across west London on a scooter.
Five gang members who made drill music videos glorifying violence have been locked up after being caught with baseball bats and machetes on their way to attack rivals.
An 11-month-old boy remains in hospital in a critical but stable condition.
Sajid Javid also vowed to prioritise police spending as he offered an olive branch to rank-and-file officers following years of sniping over budget cuts and staffing reductions.
The police have reported several cases of violent crime across the capital after bank holiday weekend bloodshed.