Juventus boss Massimiliano Allegri has sounded a rallying call as his side prepare to take their Serie A title defence to the wire – a task they must undertake without talismanic defender Giorgio Chiellini. Juve could have taken a huge step towards a seventh consecutive Scudetto when they hosted Napoli last weekend but Kalidou Koulibaly's last-minute header secured a 1-0 victory for Maurizio Sarri's side, who are now just a point behind at the summit with four matches remaining. Chiellini was replaced before half-time and, when he was asked for an update after the club confirmed the Italy centre-back had suffered a torn knee muscle, Allegri told a news conference: "His season is over." A tricky trip to face Inter in the Derby d'Italia on Saturday is up next for Juventus and the head coach told his players they must stand up and be counted. "Now is the time to demonstrate every ounce of courage and be ready for every ball and every tackle," Allegri said. "The league is all to play for and we will be doing everything within our powers to win it. "At this moment in time, everyone needs to go that extra mile in order to reach our two targets: the Scudetto and the Coppa Italia. "In football, an entire season can change in a matter of minutes. We suffered two blows against Crotone [last week's 1-1 draw] and Napoli. Maybe this weekend the opposite will happen." Allegri was keen to present a united front as such challenges loom and dismissed rumours of dressing room unrest after the damaging Napoli setback. "Regarding the locker room stories, it's never good to hear false claims like that. We're not going to let that affect us now," he said. @OfficialAllegri: "@andreabarzagli2 could start tomorrow at the San Siro. He wasn't in the right condition to play 90 minutes against Napoli."#InterJuve pic.twitter.com/lp0InOfWcP — JuventusFC (@juventusfcen) April 27, 2018 Chiellini's fellow defensive veteran Andrea Barzagli has overcome the tendon problem that left him consigned to the substitutes' bench last time out, while Allegri joked about his problems at right-back given Mattia De Sciglio (foot) and Stefano Sturaro (Achilles) remain sidelined. "Who will play at right-back? We will play two men in defence and without full-backs tomorrow," he added in a light-hearted ending to his briefing.