Ben Heneghan and Nathan Thomas have both left Bramall Lane on season-long loans.
Heneghan, 24, has joined Blackpool, whilst Thomas, 23, has penned a deal with Notts County, with both players leaving with immediate effect.
Defender Heneghan signed from Motherwell in August 2017, but made just one appearance for United last season, starting against Preston North End in the fourth round of the FA Cup in January.
Meanwhile, midfielder Thomas arrived at United from Hartlepool United in the summer of 2017 and made three appearances in all competitions for Chris Wilder's side last term. He spent time on loan at Shrewsbury Town at the end of the season.
Both were highlighted as available by boss Wilder earlier this summer.