A full-back's job in modern football is not only to shore up the defence, but also to contribute in attack. That makes the position difficult to play in, despite the lack of recognition full-backs usually get.A full-back also needs to be full of running, marauding the length of their side of the pitch. So, usually, the best full-backs are often in their 20s, with their powers beginning to wane as they cross 30.However, there are a few full-backs who have continued to perform at the highest level despite turning 30. On that note, here's a look at five full-backs above the age of 30 who are still going strong:#5 Jesus NavasJesus Navas is still going strong for Sevilla.Jesus Navas made his name as a right midfielder/winger. But since his return to Sevilla in 2017, the former Manchester City man has largely been deployed as a right-back. And Navas hasn't failed to impress at the position.The 35-year-old's speed and crossing have been two of his biggest assets, which he has used well during his second stint with Sevilla. He provided seven assists in the 2019-20 league season, and followed that up with six more in the next one. Navas has already made two assists in 11 league appearances this season.During his four-year spell with Manchester City between 2013 and 2017, Navas won a Premier League and two League Cup titles. He also captained Sevilla to the Europa League title in 2019-20.La Liga Lowdown 🧡🇪🇸⚽️@LaLigaLowdown💃Grave news for Sevilla🤕 Jesús Navas' injury against Lille was serious. He looks to be out for 2 months.#LLL 🧡🇪🇸⚽10:38 AM · Nov 4, 20218💃Grave news for Sevilla🤕 Jesús Navas' injury against Lille was serious. He looks to be out for 2 months.#LLL 🧡🇪🇸⚽ https://t.co/YIRNDIg5H6Navas recently suffered a thigh injury that will keep him out of action for eight weeks.#4 Kieran TrippierKieran Trippier is a key player for Atletico Madrid.Kieran Trippier evolved into a solid right-back during his time with Tottenham Hotspur. That helped him earn a call-up to England's 2018 FIFA World Cup squad. Trippier scored his only international goal so far in the quadrennial tournament - a free-kick in England's semi-final against Croatia.The next season, Trippier formed an integral part of the Spurs side that reached the 2018-19 Champions League final, where they went down to Liverpool. Atletico Madrid came calling, and Trippier became the first English player to represent the Rojiblancos.The 31-year-old has impressed in Spain too, with a ten-week ban due to betting-related activities being the only setback in his Atletico career so far. He also won the La Liga title with them last season.NUFC360@NUFC360Guillem Balague has said Newcastle are in talks to bring Kieran Trippier back to England.“I hear from Atletico Madrid that Newcastle are really interested in getting Trippier and they have started negotiations with his people.” #NUFC4:48 AM · Nov 5, 2021130368Guillem Balague has said Newcastle are in talks to bring Kieran Trippier back to England.“I hear from Atletico Madrid that Newcastle are really interested in getting Trippier and they have started negotiations with his people.” #NUFC https://t.co/PSfFCvWKryTrippier has been linked with a move back to England, with Manchester United and Newcastle United interested in his services.