Liverpool had a difficult 2020-21 Premier League season as they rallied late in the campaign to finish in the top four.The Reds were beset with injuries and used more than 15 defensive parings at the back. Their usually prolific front three of Roberto Firmino, Sadio Mane and Mohamed Salah weren’t at their best either.Liverpool have not done too much business this summer, as they have only added Ibrahima Konate from RB Leipzig. However, Harvey Elliot’s return from his loan spell will feel like a new signing and offer a boost. The teenager has done well in pre-season so far, and could play an important role for Liverpool next season.Several other players will be key for Liverpool next campaign as the Reds look to challenge Manchester City and Manchester United for the title after a tough 2020-21 season.Without further ado, let’s take a look at five players who will be key for Liverpool next season.#5 Trent Alexander-ArnoldThe full-back remains a key cog in the Liverpool team. Perhaps the most creative right-back in the Premier League right now, the 22-year-old has mustered 32 assists in the last three seasons combined, which is up there with the best midfielders.Alexander-Arnold came under criticism at the beginning of the year when Liverpool tumbled down the table, but he finished the season strong.Trent Alexander-Arnold has signed a new long-term contract with Liverpool until June 2025. 🔴 #LFCAlisson also in advanced talks with the club to extend his contract as he wants to stay at Liverpool.— Fabrizio Romano (@FabrizioRomano) July 30, 2021The club have put a lot of faith in him and have secured his future with a new long-term contract, so he will want to repay some of that trust next season.Having also missed out on featuring at Euro 2020 earlier this summer, Alexander-Arnold joined Liverpool’s pre-season camp earlier than most other players. This means that the full-back is ahead of the rest of the players in terms of physical conditioning, and could find his rhythm sooner.#4 Roberto FirminoRoberto Firmino in action for LiverpoolRegardless of how many goals he scores, Roberto Firmino will always be an important player in the Liverpool attack.Firmino’s ability to stitch up play in the final third by acting as a false nine allows the duo of Sadio Mane and Mohamed Salah to get into good goal-scoring positions.Roberto Firmino - Summertime Sadness pic.twitter.com/OH6UEdXI0Y— BPComps (@borgixprxdeli) July 8, 2021When the Brazilian is on song, he is a tough player to mark owing to his style of play. He often drops into spaces that neither defenders nor defensive midfielders operate in. Last season, Firmino managed nine goals and seven assists in the Premier League and will hope to improve those numbers this season.