David Moyes is not ruling out a switch to 3-5-2, but admits he has concerns over playing the system.
The Sunderland boss was considering switching formations for the trip to Stoke City last weekend, with a back three and Patrick van Aanholt and Javier Manquillo as wing-backs.
But an injury to centre-back Lamine Kone scuppered any plans of a back three.
Instead, Sunderland kept faith with their back four, with John O’Shea partnered by Papy Djilobodji in central defence, with van Aanholt and Manquillo at full-back.
Kone has since recovered from his hamstring strain picked up on international duty with the Ivory Coast and is in line for a start at West Ham United today, along with fit-again van Aanholt, who had hobbled off with an adductor injury at Stoke.
So, has their return to training forced a tactical rethink from the Sunderland boss?
Moyes said: “I’m not giving much away.
“I have a few reservations about it because of some of the personnel and the way it might work out.
“But it is not something I am ruling out. There is only the odd team that use it in the Premier League.
“We also don’t know whether West Ham will play with a back four or a back three.
“That is one of the things we are juggling with.
“We have a little bit of that in our mind.
“We are trying to get the best 11 players available out on the pitch and see if they can get a result.”
It is Sunderland’s first trip to the London Stadium, the new home of the Hammers after they left Upton Park in the summer.