Liverpool extended their lead at the top of the Premier League table following a six-goal thriller at Brentford on Saturday. Diogo Jota, Mohamed Salah and Curtis Jones all scored as the Reds travelled a rollercoaster before being held to a 3-3 draw.The sixth of seven games in 22 days, Liverpool continue a hectic period with their Champions League visit to Porto on Tuesday night.And here we look ahead to the changes Jurgen Klopp could make when his team are next in action.READ MORE: Thiago Alcantara worry emerges as Liverpool absence keenly felt Defensive rotation?The Liverpool defence had a rare off-night at the weekend, leaking three goals in a Premier League game for the first time since February.Alisson Becker will nevertheless expect to continue in goal in Portugal while Trent Alexander-Arnold is likely to remain at right-back.However, the remainder of the back line is very much in the balance.Joe Gomez and Ibrahima Konate started the first Champions League group game against AC Milan and at least one may expect to start in place of Virgil van Dijk and Joel Matip given Sunday's huge clash with Manchester City is on the horizon.And there will be a big call to make at left-back, with Andy Robertson way below par at Brentford and Kostas Tsimikas having done well in the previous two games as a starter.Join our official Liverpool fans groupConnect with Liverpool fans from around the world in our official supporters group.Keep up to date with the latest breaking news, transfer gossip and everything LFC with thousands of Reds!Join our group for FREE by clicking here!Central reservationsWith Harvey Elliott and Thiago Alcantara out and doubts over Naby Keita, there is little wriggle room for Klopp in midfield.James Milner has recovered from the cold that ruled him out last week at Norwich City and could provide a solid option alongside Fabinho and Jordan Henderson, and may open up the possibility of a change of formation to 4-2-3-1.Curtis Jones will be pressing for a third successive start after an impressive week, while Alex Oxlade-Chamberlain is the other senior alternative.Bobby backThe return to fitness of Roberto Firmino gives Liverpool a wealth of choices at the top end of the field.Firmino will be primed to start for the first time in a month, although who would drop out isn't immediately obvious.The Brazilian has been rotated with Diogo Jota down the middle but there is scope for Jota to switch to the left flank with Sadio Mane benched after a difficult evening at Brentford.Mohamed Salah appears a certainty, with Divock Origi and Takumi Minamino waiting for another opportunity.Read MoreRelated ArticlesRead MoreRelated Articles