New Blues boss Lee Clark admitted on Wednesday that negotiations are "ongoing" with Albion regarding Foster.
Cologne keeper Rensing is also believed to be on the list of possible contenders being targeted by the Baggies.
However, Foster remains their number one choice after his outstanding form when on loan from Birmingham last season.
He played a major role in West Brom finishing in the top 10 of the Premier League and was voted the club's Player of the Year.
Foster was linked strongly with a move to QPR before they signed Robert Green from West Ham, but the former Manchester United keeper has often made it clear he would be happy to remain at The Hawthorns.
Rensing will only come into the equation if attempts to sign Foster fall through.
Albion are also looking to sign a new left-back after the departure of Nicky Shorey at the end of last season.
But any hopes of bringing in Danny Rose on loan from Tottenham will have to be put on ice until the London club have resolved their managerial situation.
Midfielder Keith Andrews, who signed a short term contract with Albion after leaving Blackburn in January, is expected to move to Bolton.
Chelsea won the Europa League on Wednesday. The Blues defeated Benfica 2-1 on injury time goal from Ivanovic.
One of the top soccer cleats for control the Nike CTR360 will not let you down on the field in tight spaces.
The push for more color on their cleats, adidas has added the infrared colorway to the adiZero f50 Line.
adidas has added some color to the Predator line with this new colorway. Released on May 17. Be the first to own a pair.
Borussia Dortmund hears Wembley Calling and are headed to London for the Champions League final.
The new PUMA evoSPEED 1.2 FG. A great new soccer cleat with classic look and first time for PUMA to be on the cleat.
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
The Liverpool 2013/14 soccer jersey is available for pre-order. The Reds are eager to compete for silver next season.
Bayern Munich are kings of Germany and hope to be crowned kings of Europe at Wembley later this month!
Ajax has released their away soccer jersey for the 2013/14 season. Get in the Gear.