In mid-September he underwent an MRI but the result was negative .
Williamson 's tenure with Boston was a troubled one : his ERA with the team was 6.20 and he pitched just 20 innings in 24 appearances .
In mid-September Williamson underwent an MRI but the result was negative .
Williamson 's tenure with Boston was a troubled one : his ERA with the team was 6.20 and he pitched just 20 innings in 24 appearances .