Ighalo will only meet the rest of United's squad for the first time on Sunday because the Nigerian striker has trained alone in 'quarantine' in Manchester following his move from China as a precaution in case he was carrying the coronavirus.
The death toll from the outbreak neared 1,400 on Friday.
But despite missing United's winter training camp in Spain, Ighalo, who joined on January 31, is in line to be on the bench for the Premier League clash at Stamford Bridge with United still missing injured leading scorer Marcus Rashford.
And United manager Solskjaer says the lack of knowledge of his new team and style of play does not mean Ighalo cannot make an instant impact.
"Well, it didn't take me too long. I didn't have a training session to come on and score!" Solskjaer said on Friday.
"As a striker you get thrown on out there and it might be he'll have to come off the bench, give us a goal and he does whatever he's done.
"He'll be involved with us and travel down with us now he's out of that precautionary two week period.
"We've kept in touch with him and of course we've done our own programme, he's done his, and it was always going be a case of him having to integrate having been out in China.
"He needs to get used to the players, the team and up to speed as quick as he can.
"He's been working really hard and pinching himself at times at joining his favourite club at the age of 30. But he's earned that one and hopefully he impresses us so we can see him play."
'He's a goal-scorer'
United's signing of the former Watford striker, who has been playing in China for three years, has been subject to criticism from fans who feel he is not up to the club's standards.
But Solskjaer insisted it was necessary to strengthen United's goal-shy attack following Rashford's injury.
"We needed another forward and when we got the chance to get Odion on a loan that was for us - he's a goalscorer, he was top scorer at the Africa Cup of Nations last summer so he can help the club," Solskjaer said.
"He's a different kind of striker to what we have. He is a very professional player, a good lad and will give something to the group."
Apart from Rashford, who has a stress fracture in his back, United will still be without Paul Pogba and Scott McTominay for the game in west London, which is crucial for both clubs in the pursuit of fourth place and qualification for next season's Champions League.
United have beaten the Blues three times in a row since Solskjaer took over - in the FA Cup last season and Premier League and League Cup this term - and the manager knows another win is vital.
Defeat would leave United nine points adrift of Frank Lampard's team but Solskjaer said: "A win closes the gap to three points and that's what we've got to aim for.
"We've played them twice this season and done well. Chelsea are a good team at home but we're going to try and win the game, to give us more belief, more hope, because we need to kick on."