Philippe Coutinho will miss Liverpool's Premier League opener at Watford with a back injury while uncertainty over his future continues to rumble on.

The Brazilian handed in a transfer request on Friday, one quickly rejected by the club, as he looks to force a move to Barcelona - who have two bids for the midfielder already turned down this summer.

But Coutinho will also miss the Reds' curtain-raiser at Vicarage Road with a problem that has kept him out of training since last Friday and also leaves him a major doubt for Tuesday's trip to Hoffenheim for their Champions League play-off round first-leg.

Previewing the clash with the Hornets at his press conference on Friday morning, Liverpool manager Jürgen Klopp said that want-away Coutinho - whose official request to leave was submitted later in the day after Klopp had addressed the press - "has back problems."

He revealed that the 25-year-old has been absent from training "since last Friday" meaning that "he is not available" and "is also a doubt for Tuesday unfortunately."

Liverpool are battling a handful of injuries ahead of their opening league game, with Klopp confirming that striker Daniel Sturridge will also be absent through injury.

The England international sustained a thigh injury in a pre-season trip to Germany but could be back when Liverpool return to Klopp's homeland to face Hoffenheim.

Klopp hailed Sturridge's "fantastic pre-season" form but noted that he suffered from "a little thing", adding: "He is close [to being fit] - he was already close for this weekend, but now for Tuesday it is pretty sure he is ready."

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I have some hard decisions for Watford line-up, says Klopp

In addition to Coutinho and Sturridge, Liverpool will be without midfielder Adam Lallana - out for at least two months with a thigh injury - and right-back Nathaniel Clyne, sidelined by a back issue.

The Reds boss said that Lallana's injury is "really unlucky" and said that Clyne has suffered from his "problem" since "the first day."

"And now Phil with the back, so that makes it four players," Klopp continued, calling it "not too cool" that he will be short of so many key players but insisting that he has "hard decisions" to make because "a few players really showed up in pre-season."

Klopp explained that while Liverpool's stand-out performers "are young" and "have to prove their quality in the Premier League", their performances mean he has "to make hard decisions" as to who is included in the 18-man match-day squad.

He added: "But I could go into the season with this squad, that's no problem. That's what we will do and then we will see what happens [in the transfer market] by the 31st."

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Danny Ings to feature for Reds' under-23s

Captain Jordan Henderson will be available after returning from an illness which kept him out of the club's final pre-season friendly in Dublin last weekend, Klopp stating his absence was to avoid "any risk."

"The doc told me he was not 100 per-cent so we left him at home, but he was part of all sessions and was all good," Klopp said.

With Coutinho and Lallana both out, Henderson is expected to make up a three-man midfield with Emre Can and Gini Wijnaldum his most likely partners.

James Milner is another potential option in the centre with summer signing Andrew Robertson competing for a debut at left-back and the recently-rejuvenated Alberto Moreno also battling for a start.

Trent Alexander-Arnold will likely start at right-back given Clyne's absence from pre-season in its entirety, with Mohamed Salah to make up a front three alongside Roberto Firmino and Sadio Mané.

Another player who will play no part is Danny Ings, who will continue his ongoing recovery from a lengthy knee injury with a cameo for Liverpool's Under-23s at Swansea City on Friday night.

Ings missed almost all of last season after undergoing knee surgery, a year after doing his cruciate ligament in the opposite knee, but will maintain his search for fitness with the reserves in Wales.

Klopp said that Ings "needs games" and has been "unlucky" with his injury because he "looked really good in the sessions" but revealed: "When he could be 100 per-cent part of the pre-season games, there was no time for us to really test and give him five or 10 minutes. We had to do it differently. It was not too cool but it was the situation."

But the German said that the 25-year-old frontman "is ready to go" and is "as fit as he can be in this moment" because he has "no problem" with his injury, insisting that Ings needs several outings to build up his fitness before he can be a first-team option again.