MANCHESTER, England, Sept 20 (Reuters) - Manchester United ( MANU ) breathed life into their stuttering Premier League season when goals from Bruno Fernandes and Casemiro earned them a thrilling 2-1 home victory over Chelsea on Saturday.

A frantic first half got off to the worst possible start for Chelsea when goalkeeper Robert Sanchez was sent off in the fifth minute for a flying lunge at Bryan Mbeumo, up-ending the United forward when he was through on goal.

The hosts, with just one victory to their name previously this campaign, made their numerical advantage count, with Fernandes and Casemiro putting United 2-0 in front inside 37 minutes.

Casemiro's needless dismissal just before halftime evened up the numbers and gave Chelsea a way back into the contest but Trevoh Chalobah's late header was all the visitors could muster as a nervy United held on for a vital three points.

The pressure has been mounting on United coach Ruben Amorim after defeat in the Manchester derby last weekend left the Portuguese with a win record of just eight from 31 league games since taking charge last November.

The visit of Chelsea offered Amorim the opportunity to start rectifying that meagre return, with the Blues winless at Old Trafford since 2013. Sanchez's rash tackle aided the beleaguered United manager's cause a great deal.

Along with the added setback of Cole Palmer being withdrawn through injury, Chelsea boss Enzo Maresca was forced into an early reshuffle, making three substitutions in the first 21 minutes, the earliest a side has ever done that in a Premier League game.

It was not long before Fernandes added to Old Trafford's euphoria in the driving Manchester rain, the skipper nudging home his 100th goal for United in all competitions.

Casemiro then seemingly put United in an unassailable position after determined work from Luke Shaw to keep alive the attack, the veteran Brazilian heading his first goal of the season.

A second booking soon turned Casemiro from hero to villain as he became the first player to score and be sent off in the first half of a Premier League match since Emmanuel Adebayor for Spurs against Arsenal in November 2012.

Even when chasing the game, Chelsea offered very little attacking threat until Chalobah's header 10 minutes from time. United looked ragged from there on in, but Altay Bayindir remained largely untroubled in the home goal as the hosts held on.