The left-back has returned to the Blues’ starting XI after being rested for the midweek win over Barnsley in the third-round of the Carabao Cup as head coach Frank Lampard rotated his squad.
In came Emerson Palmieri for a rare appearance, while £50m summer signing Ben Chilwell made his debut as a second-half substitute.
With competition for places fierce, Alonso hasn’t exactly done his chances of keeping his place in the side any good as he was at fault for the visitors falling behind inside the opening 10 minutes.
His casual headed clearance lacked any purpose and the Baggies picked up on the loose ball and launched a counter-attack.
Callum Robinson eventually collected a pass and drilled an effort into the bottom corner – past the outstretched arm of Willy Caballero – who is in goal instead of Kepa Arrizabalaga.
Replays did suggest that Caballero may have done better with the effort.
However, there’s nothing that can help Alonso escape the ire of many Chelsea supporters.
Take a look at what’s been said on Twitter…
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It would get worse for Alonso and company as the first-half wore on.
Robinson got on the scoresheet again, while Kyle Bartley made it 3-0 as the Blues were punished for slack marking at a corner.