Injury scare for England ahead of SA Tour
Joseph was on crutches after suffering what appeared to be an issue with his left ankle having been caught awkwardly at a ruck shortly before the half-hour mark.
The outside centre, a fixture in the England team since 2015, was in obvious discomfort.
England coach Eddie Jones will await news on a setback that could prevent Joseph from adding to his 40 caps when the national team tour South Africa in June.
It was a worrying development for injury-hit Bath, whose season continued to deteriorate as they slumped to a fifth defeat in six Premiership matches.
Saracens had the bonus point in the bank in the 49th minute when Owen Farrell scored and they are now guaranteed a top-four finish.
Sam Simmonds bagged a hat-trick as Premiership leaders Exeter clinched a home semi-final with a 45-5 rout of London Irish.
Simmonds' heroics ensured Premiership champions Exeter booked themselves home advantage in the play-offs, with Ben Moon, Mitch Lees and Jack Yeandle also scoring tries.
Exeter took a step closer to topping the Premiership's regular-season table, maintaining their eight-point advantage over second-placed Saracens.
Irish's 17th defeat in 20 league matches leaves the bottom club staring down the barrel of a second Premiership relegation in three years.
New boss Declan Kidney surely cannot now save the Exiles, who trail Worcester by nine points with only a maximum 10 on offer in their final two matches.
Prolific England number eight Simmonds took his Premiership try tally to 12 for the season – just one behind the league's top scorer, Worcester's Josh Adams.
Flyhalf Gareth Steenson ended the day with a flawless 15-point return from the tee