Pedro made a sensational start to his Chelsea career as the Blues scooped their first three points of the season, beating WBA in a five goal thriller at the Hawthorns.
John Terry was sent off, the Baggies missed a penalty and terrible defending conspired to make this a thriller of a game.
The champions could have been three down before Pedro, on his debut from Barcelona toe-poked the opener on 13 minutes.
James Morrison had by now already seen his penalty saved by Thibaut Courtois with two other chances for the Baggies going begging.
Diego Costa doubled the lead before Morrison brought the deficient down to one.
Cesar Azpilicueta restored the two-goal margin before Terry was handed a red card for hauling back Salomon Rondon, .
Morrison hit his brace with a glancing header but the Blues hung on to the lead to record their first win in three Premier League matches.
Chelsea started off ponderously, with their defence all over the place on four minutes when Chris Brunt ghosted in and tucked home behind the back four, but Thibaut Courtois was quick to snuff out the effort. A minute later and The Blues, playing in all black carved out an opening which saw Diego Costa flash a left footer across Boaz Myhill's body, but just wide of goal.
But on 13 minutes, Chelsea's Nemanja Matic was suckered into a penalty, with Callum McManaman the victim. Up stepped James Morrison who smashed the ball from the spit kick only to see Courtois stay strong and propel the ball over his crossbar.
Craig Dawson then headed over from close range as Chelsea struggled to get a grip on the game.
Ironically, with their second attempt on goal, they scored, Eden Hazard clipped the ball to new boy Pedro, who took one touch before toe-poking a weak left footer goal-bound. It took a slight deflection off Jonas Olsson and slipped past Myhill.
The Blues then increased their lead 10 minutes later. Following a quick breakaway from a WBA cleared corner, the ball zipped across the pi he twice effort William found the feet of Pedro who arrowed the ball across the six-hard box, where in-running Costa slid it home.
Chelsea's fans comical chant of 'we are staying up', while funny, indicated a sense of relief that normal service for the champions appeared to be restored.
But defensive fragility at the heart of the Chelsea side remains, and when Cesc Fabregas, on 36 minutes, gave the ball alway just outside their own area, the ball was quickly dispatched to the far post where Salomon Rondon cut the ball back to unmarked Morrison who buried the ball past Courtois to make it 2-1.
Twice Willian should have scored as the Blues's counter-attack policy almost reaped benefit, both times the Brazil midfielder scored the ball wide of Muhill's goal.
Number three duly came three minutes before the break. This time it was a calm, collected build-up, which eventually saw, from a Costa knock-on left-back, Cesar Azpilicutea, slot a scuffed right footed effort from the edge of the WBA penalty area past Myhill.
Disaster struck for Chelsea on 54 minutes when John Terry was red-carded for hauling back Rondon at the edge of the his penalty area.
Calttenburg flashed a yellow card first, but that must have been an error as Terry had not had yellow-carded in the match.
Willian was sacrificed as Gary Cahill entered the fray.
Bug that did not help as three minutes later Morrision glanced in a deep James McClean cross and the ball bulleted past Courtois to make it 3-2.
McManaman almost equalised when he twisted the blood of Ivanovic before dumping the defender on the ground with his mazy skill. Luckily for the Serbia full-back, his angled curler inched wide of goal on 72 minutes.
Costa had an good chance but skied his effort - it was his last action as he was replaced by Jose Mourinho for Radamel Falcao for the last 15 minutes. The Colombia hit man scuffed his first effort from a Pedro pass with the goal beckoning.
Mourinho decided to shore up the midfield by bringing in Mikel for the impressive debutant Pedro with seven minutes left in the clock.
It was enough and the Blues ran down the clock to secure all the points.
Teams
Chelsea: Courtois, Ivanovic, Zouma, Terry, Azpilicueta, Matic, Fabregas, Pedro, Willian, Hazard, Diego Costa.
Subs Begovic, Cahill, Mikel, Loftus-Cheek, Traore, Remy, Falcao.
WBA: Myhill, Olsson, Yacob, Morrison, Brunt, McClean, McManaman, McAuley, Flectcher, Dawson, Rondon
Subs: Rose, Chester, Lexcott, Gardner, Anichebe, Lambert, Gnabry
Referee Mark Clatternberg