And the head coach has pledged to ‘find the spark’ to ignite the loanee’s underwhelming Pompey career.
Cowley told The News: ‘I’ve got the best out of Tyler once – and will try to keep working with him to find the spark that he needs to play to his best.
‘He scored against Crewe in the previous game he started and then picked up that ankle injury, which probably just stopped his momentum a little. Unfortunately, that’s the way it has gone for him.
‘We haven’t seen the best of him, that’s obvious to say.
‘I’m not going to criticise my players and I never will, not to you guys, and I don’t mean that disrespectfully.
‘Being a professional footballer is a tough job, especially at a big club like Pompey where there’s a lot of noise, so I’m not going to create more.
‘Tyler has to keep working. His attitude, work ethic and willingness for the team is, without doubt, there, but it has not happened for him at this point.’
Cowley had hoped Walker would provide the cutting edge so glaringly absent from his side in the first half of the season.