The hosts got the first chance of the match less than 10 minutes in, when Fernando Torres broke free of the Newcastle defence. The striker then found John Obi Mikel, but the midfielder's shot went high and wide.
The deadlock was broken after 22 minutes when, Torres went down under the challenge of Vurnon Anita in the box. The referee blew for the penalty - Chelsea's third in as many games - and Eden Hazard made no mistake.
The Blues almost got a second with 10 minutes left of the half, Branislav Ivanovic nearly adding to his two goals already this season, but Krul was equal to it.
Newcastle enjoyed their best chances of the half towards the end of it. First, Papiss Cisse's cross found Ba, but the Senegal striker could only head over, and then Danny Simpson caught David Luiz in possession, feeding Cisse whose powerful strike was well saved by Petr Cech.
It was Chelsea who got the late goal, however, as Torres poked his effort past Krul in the second minute of stoppage time.