Reports claimed during the week that Rashford had picked up an injury during last weekend’s win over Huddersfield Town and would be closely monitored by medical staff.
The source of Herrera’s injury is less clear but the Spaniard, following a 20 minute cameo against Tottenham Hotspur a few days earlier, wasn’t included in the squad against Huddersfield.
And Mourinho has confirmed that the pair were absent at St James’ Park as they continue to recover full fitness, noting he didn’t know when they would return.
Mourinho has told Sky that Herrera and Rashford have both got muscle injuries. Says he doesn't know how long they will be out.
— Rob Dawson (@RobDawsonESPN) February 11, 2018
Herrera’s performances have mainly frustrated supporters this season but his tenacious, warrior-like influence in the middle would have come in handy against Jonjo Shelvey, who was fantastic for the hosts, as Paul Pogba sauntered around the pitch with an injury clearly holding back and Nemanja Matic was left stranded.
United have proven time and time again this season that their best performances come with a midfield trio and Herrera, with Marouane Fellaini injured until late March, needs to prove to his boss that he can consistently deliver alongside Matic and Pogba, giving the latter a chance to play down the left channel and impact games going forward.