The Chile international made a ludicrous two-footed challenge on Luke Varney just before the half-hour mark at Bloomfield Road, reducing the Baggies to nine men after Pablo Ibanez was given his marching orders under harsh circumstances earlier.
di Matteo said the refereeing of Michael Oliver left a lot to be desired but did agree with the decision to send Jara from the pitch.
"It would be nice to see a good football game but obviously it's been destroyed by events on the night," he said.
"The first incident probably was a penalty but in my opinion it's not a sending off, my player is goalside and close to goal.
"The second one (Jara's dismissal) I think he called it right, the referee. The player lost his head a bit, after the first decision, but he made a terrible tackle and made a mistake."