Usually the supplier’s power is considered to be low especially in а big retail market within UK. As we already know the products provided by suppliers are quite similar in features which give buyer а chance to negotiate. Sainsbury’s has а good reputation of being а trusted brand and most suppliers find it profitable to be involved with their business as they have large marketing scale.
As а result, suppliers has less scope to negotiate too much knowingly Sainsbury’s has the privilege to switch to another supplier because of their big brand image. At some points suppliers may have got some power to negotiate when they can introduce unique products to the market. Some times also what happens suppliers are by themselves are huge as а company. For example P&G, Unilever, Cadbury etc in those cases if companies like Sainsbury’s don’t sell their products may face huge negative effects on their sales figures.