The loan deals of Sunderland striker David Dowson and defender Peter Hartley have both been extended until the end of the season following agreement between the two clubs.
During their initial one month's loan, they helped to kick-start Chesterfield's season by contributing to three consecutive victories.
David Dowson - goalscorer against Brentford
Chesterfield manager Lee Richardson said: "We are pleased that the two Sunderland lads are staying with us some more as they continue to provide healthy competition in the squad and this helps keep everyone on their toes."
Peter Hartley getting stuck in at Rochdale
Peter Hartley said: "We are certainly enjoying our time with Chesterfield and welcome this opportunity to extend our loan spells during a period when the pressure is on to achieve promotion."
Peter Hartley (19) has been at Sunderland since 2000, where he has worked up through the youth teams and is something of a regular in the reserves.He made his debut for Sunderland in January 2007.
Striker David Dowson (19), who has been a prolific striker for Sunderland's Under 18s and youth teams, signed a professional contract with Sunderland in the summer of 2007 and is also a regular in the reserve side.
