Beattie was fit to play by the start of the 1977–78 season, but a knee injury sustained in a league match led to him withdrawing from the England squad to face Luxembourg. Further investigation revealed he had damaged cartilage in his knee, which required an operation. Having had three weeks' recuperation and a cortisone injection, he was restored to the Ipswich squad in time to play in the third round UEFA Cup home leg against FC Barcelona. Ipswich won the fixture 3–0, and even though he suffered a reaction in his knee, he insisted he was able to play in the away leg. Robson disagreed, and Beattie was left out of the side for the game; Ipswich were knocked out on penalties. Cortisone injections became commonplace for Beattie, who returned to the team in time for the FA Cup fourth-round victory against Hartlepool. Although Ipswich's form in the league was poor, they were safe from relegation by the time they faced West Bromwich Albion in the FA Cup semi-final at Highbury, a game for which Beattie was given the all-clear. A 3–1 victory saw Ipswich into the final, yet the next day his knee was once again swollen and his participation in the final was in jeopardy. According to Beattie, "the boss secretly told me that if I felt fit enough to play then I was in". Robson did not announce the Cup final team until the last minute: it included a formation change to include five midfielders and Paul Mariner as a lone striker – and Beattie in defence. Roger Osborne's late goal for Ipswich was the only score of the game, and they won the trophy. Beattie had three cortisone injections to get through the final. Following the cup final success, he and teammates Robin Turner and David Geddis were awarded the freedom of Carlisle. Beattie had represented Ipswich 21 times during the course of the season, without scoring a goal.