Johnstone left Old Trafford in July 2018 after 15 years associated with Manchester United and has not missed a single league game for the Baggies since.
The Preston-born 27-year-old believes leaving United aged 25 was too late and not playing regularly hindered his career.
Dean Henderson has been urged to leave the club by West Brom goalkeeper Sam Johnstone
Henderson (right) made his first ever league appearance for United against Southampton
And former England U20 international urged Henderson – currently behind David de Gea in the pecking order – to leave for the sake of his career.
He told the Goalkeepers’ Union podcast: ‘I couldn’t think of anything worse than being there (at Old Trafford) and not playing. You want to be playing as a ‘keeper.
‘I was asked last week whether I missed United. I said ‘no’. I’m playing in the Premier League with West Brom. Deano had a great loan spell at Sheffield United, I can’t see him happy sitting down; all Dean wants to do is keep playing. It’s stalled.
Sam Johnstone left Old Trafford in 2018 aged 25 after 15 years associated with the club
Henderson’s former United team-mate reckons the 23-year-old must leave to further his career
‘Dean’s very young, he probably has to be patient but how long is your career? It flies by. I was probably too patient leaving at 25 – it’s a tough situation. I’m sure he is working hard every day. You train all week to play on a Saturday. That’s what you are in football for.
‘It will be difficult for him to be No 1, everyone knows what De Gea is capable of. United is such a big club and the pressure there is massive. You are fighting the best keepers all over the world.’
Once-capped England senior international Henderson played week-in, week-out in League One, the Championship and the Premier League on loan at Shrewsbury and Sheffield United respectively.
Red Devils boss Ole Gunnar Solskjaer has said he views Henderson as the club’s future no 1
But David de Gea, who went off injured against Southampton, is his current first choice in goal
But he has found it difficult breaking into the side ahead of star name David de Gea, only playing four times in all competitions so far this season.
Red Devils manager Ole Gunnar Solskjaer has confirmed he views Henderson as the club’s future no 1.
But Henderson may look for a temporary or permanent move away to ensure regular game time and the natural progression that entails.