Exeter’s biggest victory here looked at one point as unlikely as Worcester mounting a title challenge. They were 13-0 down and were being given the runaround by a team buoyed by the return of the England flanker Sam Underhill, who thwarted the Exeter’s first attack by winning a penalty on his own line. England have yet to find their feet in this year’s Six Nations so the return of Underhill, performing under the gaze of the Lions head coach, Warren Gatland, was timely. He was playing his first match for two months after recovering from a hip injury and lasted 48 minutes before being replaced. Bath’s problem was they faded collectively not long after. They led 16-12 on the hour but by then the irrepressible rugby they had produced at the start, using the width of the pitch to get in behind Exeter and stretch the champions by getting the ball away quickly from the breakdown, had been downgraded to all-out defence. The hands of Josh Matavesi and the threat of their back three complemented a mobile pack, but discipline is essential against Exeter and the home side gave them an in by conceding penalties. Rhys Priestland extended his run of successful goal-kicks in the Premiership to 36, his two penalties in the opening quarter bookending a try by the wing Ruaridh McConnochie, which the outside-half engineered with a weighted cross-kick to the right wing, where Jack Maunder was beaten in the air and Tom O’Flaherty overpowered. Bath were in their pomp then, playing with a swagger generated by three successive victories, but a couple of unforced errors and a penalty led to them defending a lineout five metres from their line. For once, Exeter did not drive a maul and the deception worked as Maunder’s run was supported by O’Flaherty coming into midfield from his wing. Another penalty and lineout gave Exeter the chance to take the lead as Sam Simmonds, unwanted by England, finished a 15-phase move to score his 13th try of the league season, four short of the record with 10 rounds to go, but Joe Simmonds, normally as accurate as Priestland, pulled his conversion to the left. Bath extended their lead to four points 14 minutes into the second half with Priestland’s third penalty. But the game was now being played on Exeter’s terms. After Will Muir wasted an opportunity by holding on to the ball rather than passing inside to Ben Spencer and Taulupe Faletau’s chip to the line was followed by a soft penalty their attacking threat melted. Exeter scored four tries in the final 20 minutes, the first three by the second-rows Sam Skinner and Jonny Gray as they took play through multiple phases, pepped by the introduction of the scrum-half Stu Townsend, who gave the tiring Bath forwards no chance to catch their breath. O’Flaherty finished off the game with a flourish and what had threatened to be a third successive defeat turned into their biggest victory here and five points. Bath will probably have to do without Underhill for the next couple of weeks as he waits for the call of his country. “I have no idea what England are thinking,” said Stuart Hooper, the Bath director of rugby, although the number of penalties England conceded in Cardiff for failing to stay on their feet after a tackle suggests the back-rower will be at Twickenham rather than Newcastle. Underhill’s replacement, Miles Reid, won a penalty off the Scotland second-row Gray shortly after coming on, but the topsy-turvy nature of the game summed up the season. “The top four is definitely doable,” said Hooper. “We showed we have the game to challenge the best team in the league, but we have to get the little things right. They amount to a lot when you add them up.”