• Left-back to miss Europa League first leg against St Étienne • José Mourinho to stick with back four who kept out Watford

Luke Shaw is fighting to convince José Mourinho of his worth, with the left-back likely to be left out of Manchester United’s squad for Thursday’s Europa League home game with St Étienne.

The manager said Shaw would not be in his starting XI and it could be the fourth consecutive match-day squad from which the 21-year-old has been excluded. His last appearance was in the 4-0 FA Cup win over Wigan Athletic on 29 January.

Mourinho said: “He’s not playing because my team is playing well and I am happy with my back four, and I’m going to repeat Valencia, Bailly, Smalling, Blind.”

That was the defence for Saturday’s 2-0 home win over Watford but Shaw is hopeful of being named in the team for Sunday’s FA Cup tie at Blackburn Rovers.

Mourinho’s view is that Shaw has to fight his way back. He dropped Henrikh Mkhitaryan and Anthony Martial earlier this season and each showed he deserved to be selected again.

United face St Étienne with Mourinho concerned progress in the competition will cause “trouble” for United later in the season, with postponed Premier League matches causing a fixture pile-up. United play Southampton in the EFL Cup final on 26 February.

“We know that our situation is really complicated,” Mourinho said. “We know the Europa League is also a competition where we play on Thursdays and that makes it even more difficult for us. The accumulation of FA Cup and League Cup and the match postponements makes it really hard. If we progress in the competitions we will be in trouble in May.”

United are sixth but only four points behind second-placed Manchester City. “The plus is another opportunity to qualify for the Champions League,” the manager said. “We have two doors still open. One is the Europa League, but we know we are in the last 32 not even the last eight or four, so there is a long way to go. In the Premier League the door is also open but we still have a long way to go.

“It’s even harder the fact the match against Man City is postponed [owing to EFL final]. If we win against Blackburn, the match against Southampton will be also postponed. We never got a Monday fixture to have an extra day’s rest so, for example, Middlesbrough [19 March] will be played Sunday 12 o’clock.”

Mourinho added: “April and May will be very hard if we progress in the competitions.”

Facebook Twitter Pinterest Florentin Pogba has had his hair shaved to leave his and his brother Paul’s shirt numbers visible. Composite: PA

The match against St Étienne pits Paul Pogba against his older brother, 26-year-old Florentin, for the first time. Mourinho said: “We spoke about it in a funny way. It’s a nice destiny. Only mum Pogba is a little bit in trouble, which is normal. It’s difficult for the lady to choose, it’s impossible. I know from Paul that the mum wants a draw but next week one son will be happy and another one will be sad. For the mum it’s a bit of a problem, but they will enjoy playing against each other. Paul will enjoy it and Florentin the same, it’s a good thing.”

Florentin has had his hair shaved to leave his and Paul’s shirt numbers visible on his scalp. “The 19 is my squad number and the six is for him,” he said. “It’s going to be a magical moment and I hope he and I enjoy it the best we can. No anguish at all, absolute excitement for me. No worries at all. It’s all positive. I’m really passionate about the game and I cannot wait to play in this historic stadium and to play against my little brother, so it’ll be fun.” Their mother, Yeo, is due to attend both legs of the tie.

Manchester United (4-2-3-1): Romero; Valencia, Smalling, Bailly, Blind; Pogba, Ander Herrera; Mata, Mkhitaryan, Martial; Rashford.

Subs from: De Gea, Shaw, Darmian, Ibrahimovic, Schweinsteiger, Fosu-Mensah, Tuanzebe, Lingard, Fellaini.

Injured: Rojo (knock), Rooney, Carrick (muscular), Jones (foot).

St Étienne (4-2-3-1): Ruffier; Malcuit, Théophile-Catherine, Perrin, Pogba; Veretout, Pajot; Hamouma, Saivet, Monnet-Paquet; Roux.

Subs from: Polomat, Lemoine, Selnaes, Moulin, Guendouz, Lacroix, Mbengue, Dabo, Soderlund

Injured: Beric (hamstring), Tannane (hernia)

Referee: Pavel Kralovec (Cz)