Let me explain it to you then.
Against Blackpool, Walker (supposedly a striker) played for 65 minutes without scoring. He was then replaced by non other than Matty Godden, who played for 25 minutes and scored 1 goal. (Oh the irony) Take a minute to process that thought!
You still with me? ... . Bare with
In the last 3 years or so, Mr Walker has appeared approximately 83 times for us and league 1 Plymouth where he scored a grand total of 11 goals, a rough average of 1 goal every 7.5 appearances. While also gaining something of a reputation from both city and Plymouth fans for being lazy and half arsed.
Mr Godden has appeared 101 times for us, and amassed a creditable 40 goals in that time, which gives him an rough average of 1 goal every 2.5 appearances, and become something of a terrace hero at the same time, and even has his own song.
(Which Walker doesn't have, ...unless you include the chant "get that useless twat Walker off"
Just for comparison, Gyokeres has 108 appearances for us, and also scored 40 goals, and is valued in excess of £20 million, surely by your logic, he should also be replaced by Walker after missing so many chances against Reading.
Now Mr Walker may have impressed you with his 65 minutes of fruitless effort against Blackpool, and I'm sure the fact that he ran around a bit more than usual has absolutely nothing whatsoever to do with him being out of contract in 2 games time.
Your completely entitled to your opinion of course, ....as unique as it is.
But I hope some of the above will give you some food for thought.
Have a good one