LONDON:With 24 bookings in two-and-a-bit seasons, moody Chelsea striker Diego Costa is used to living on the edge in English football.And nowhere is his brittle temperament seemingly put to the test more than in matches against Liverpool.A stamp on Emre Can that earned Costa a retrospective three-match ban. The numerous bust-ups with Martin Skrtel. The forehead-on-forehead confrontation with Steven Gerrard. It doesn’t take much to rile Costa, but there’s something about Liverpool that really fires up the often-pilloried Spain international.So expect plenty of scrutiny on Costa when the two teams meet in tonight’s fixture of the English Premier League, which is the highlight of the fifth round of games.The debate is on regarding Costa: Will he finish the season with more goals than yellow cards? It’s a close-run thing at the moment.He is back to his best in front of goal, netting four goals in four games in Chelsea’s unbeaten start to the league campaign that has seen the team earn 10 points from a possible 12. In the 2-2 draw against Swansea on Sunday, Costa scored both of Chelsea’s goals and was almost impossible to keep down.Costa is also keeping match officials busy by getting three yellow cards, and ran the risk of seeing those turn into red with a studs-first challenge against West Ham and by throwing himself theatrically to the ground against Watford and Swansea.Costa, put simply, is never far from a flashpoint.”If you are in a friendly-game mood, then you have no chance,” Liverpool manager Juergen Klopp said of Costa. “He is a real warrior on the pitch.”There’s rarely a news conference with Chelsea manager Antonio Conte that doesn’t involve a line of questioning on Costa. Conte says the striker is targeted and it is easy to see why given Costa’s inability to resist reacting to goading by opposition players.”Diego is growing in these situations in the last game, he showed great attitude,” Conte said yesterday. “He is passionate but I want him to put his passion into the football in the right way.”It’s one of the many subplots in what could be a thrilling game under the Stamford Bridge lights, considering the start to the season made by Chelsea and Liverpool.Liverpool has scored four goals in each of their wins over both Arsenal and Leicester, and also gained a point from a draw at Tottenham. Aside from a disappointing 2-0 loss at Burnley, Klopp’s side has been impressive especially the fluid forward line of Philippe Coutinho, Roberto Firmino and new signing Sadio Mane.Only Manchester City, who has won all four of their games, has more points than Chelsea so far this season.And if Costa shows passion on the field, Klopp and Conte are possibly the most animated Premier League coaches on the touchline. Like in last weekend’s Manchester derby when Pep Guardiola and Jose Mourinho went head to head, there could be as much focus on the coaches’ technical area as on the field at Stamford Bridge.Here are some other things to watch out for this weekend:LUIZ STARTSDavid Luiz will make his first appearance in his second spell at Chelsea after Conte confirmed yesterday that the Brazilian will replace injured John Terry at centre back.Terry hurt his ankle against Swansea and was ruled out for 10 days.Luiz was signed from Paris Saint-Germain for a reported 32 million pounds (US$42 million) on the final day of the transfer window, about 20 million pounds less than Chelsea sold him to PSG for in 2014.CITY’S RUNMan City puts their winning start to the season on the line at home to Bournemouth, having taken their run of successive victories to seven by beating Borussia Moenchengladbach 4-0 in the Champions League on Wednesday.Pep Guardiola still hasn’t tasted defeat as City manager.After his hat-trick against Moenchengladbach, Sergio Aguero drops out of the team for tomorrow’s match. He is serving the second match of a three-game domestic suspension for elbowing an opponent.OTHER GAMESManchester United manager Jose Mourinho will hope a Europa League match at Feyenoord yesterday doesn’t take too much out of the team for a Premier League match at Watford on Sunday.Also Sunday, it’s: Tottenham vs Sunderland; Crystal Palace vs Stoke; and Southampton vs Swansea.Tomorrow it’s Hull vs Arsenal; Leicester vs Burnley; West Bromwich Albion vs West Ham and Everton vs Middlesbrough.