SYDNEY midfielder Jake Lloyd has been an early casualty as the Swans face a switched-on Hawthorn at the SCG.

He was joined on the back row of the Swans' bench by teammate Sam Reid who also suffered a head knock in a tackle, the big man going down in the second quarter.

Lloyd spent little more than a minute on the ground before his night ended early.

While being tackled by former Swan Tom Mitchell, Lloyd’s head crashed into Liam Shiels’ knee, leaving the 23-year-old lying prone on the turf.

He was assisted off the ground where he received attention but failed a concussion test and returned to the Swans’ bench later in the term in his tracksuit.

Lloyd has been enjoying his best season this year, averaging 30 disposals a match.

Reid left the ground during the second term after his head hit the ground in a Shaun Burgoyne tackle and didn't come back out of the rooms until well into the third quarter.

He walked the boundary for a minute accompanied by a member of Sydney's medical staff but went to the bench and put on a tracksuit, joining Lloyd as a spectator for the rest of the match.