West Brom engine room where game won or lost

And it’s fair to say both Dean Smith and Sam Allardyce have some big calls to make when it comes to who they deploy in the middle of the park for this derby day showdown.

For Allardyce in particular there is plenty to ponder with the boss likely to be weighing up three different systems.

The Baggies found their feet under the 66-year-old from February through to March playing a 4-3-3 formation.

With Okay Yokuslu sitting in front of the back four and Conor Gallagher and Ainsley Maitland-Niles either side, the team became very hard to break down.

But Allardyce switched to a 3-5-2 for the win at Chelsea with his team impressing for half-an-hour.

Following Thiago Silva’s red card they shifted to a 4-2-3-1 that led to their five-goal haul. That system was also used for the emphatic win over Southampton.

But against Leicester, it’s fair to say they had been worked out, with the Baggies completely overrun in midfield.

Allardyce may feel they need the security of an extra body in the middle of the park tomorrow.

That could see Gallagher recalled to the side in a 4-3-3.

But if he is, one of Matt Phillips or Callum Robinson will likely be dropped.

That would be harsh on either with Phillips having impressed over the last few weeks while Robinson has found his goalscoring touch.

Alternatively, Phillips could be moved from the wing into a central position, with Robinson keeping his place on the left flank and Matheus Pereira moving to the right.

Moving to a 4-3-3 seems the likely option, but Allardyce could also get an extra man in the middle by switching to the 3-5-2 first seen at Chelsea.

Again you’d expect Robinson to drop out, with Phillips or Gallagher moving into central midfield and Semi Ajayi joining Dara O’Shea and Kyle Bartley at the heart of the defence.

When Villa won 3-0 at The Hawthorns in December their first XI largely picked itself but that is far from the case now, particularly in midfield where Smith has struggled to find an effective mix.

John McGinn, Douglas Luiz, Marvelous Nakamba, Jacob Ramsey and Ross Barkley have all been used in various combinations without the boss ever quite hitting on the right formula. With Jack Grealish absent, Villa have been consistently poor in possession, on occasions alarmingly so.

Zimbabwe international Nakamba has started the last two matches but may find his place at risk after an erratic performance in the midweek defeat to Manchester City. McGinn will keep his place after ending a six-month wait for a Premier League goal against the league leaders, with Luiz sitting deep.

Smith must then decide whether to move Ramsey back inside after the teenager started on the wing against City, or hand one final chance to Barkley.

The on-loan Chelsea midfielder’s season has rapidly become a nightmare. When Barkley first joined last September, Smith promised to get him back into the England team. Currently, he cannot get into Villa’s, his last start coming in the 2-1 defeat to Leicester more than two months ago.

“Ross had a hamstring injury and initially did OK when he came back. But then his form dropped off a little bit and he became frustrated with that,” said Smith. “We have been working together and the last three or four weeks certainly in training he is pushing for a starting place now.”