Goalkeeper Bobby Olejnik made a fine save inside the first five minutes to tip over a fierce Ross McCormack free-kick as Leeds made a positive start to the fixture at London Road. On eight minutes the breakthrough was made as McCormack found Luciano BECCHIO whose left-footed shot was powerful enough to beat Olejnik.
Posh responded well and came close to a leveller on 12 minutes as a superb corner from Grant McCann was nearly forced home by a combination of Zakuani and Brisley, but Kenny kept the effort out and then the Whites cleared.
An in-swinging free-kick from McCann was glanced just past the post by Shaun Brisley as Posh again came close. Sinclair became the first player to be cautioned on 28 minutes as he went in late on Peltier.
On 33 minutes, Ross McCormack planted a header just past the post after a good run and cross from Peltier. The same Leeds player then struck a free-kick into the wall after Zakuani had been cautioned for a tug on Varney.
At the start of the second period, Olejnik denied David Norris as the rain began to fall again at London Road. Moments later and Kenny was called upon to make a save at the other end as he pushed away a fierce Tomlin strike from distance.
It was 2-0 to the visitors on 50 minutes as McCormack picked out an unmarked BECCHIO at the far post and he made no mistake, planting a header past Olejnik from close-range.
Sinclair was replaced by Paul Taylor on 63 minutes. Kenny denied Tomlin once more when his header was tipped over by the former Queens Park Rangers shot-stopper.
The deficit was halved on 73 minutes and it was a stunning volley from Michael BOSTWICK who notched his first goal for the club in fine style, firing home from the edge of the area.
The goal lifted the hosts and they piled forward in search of an equaliser with Swanson particularly prominent in everything good that Posh were trying to put together in the attacking third.
Zakuani headed a McCann corner kick wide of the target on 85 minutes.
Final Score: Posh 1-2 Leeds United
Posh: Olejnik, Alcock (sub Little 61min), Brisley, Zakuani, Ntlhe, Frecklington (sub Swanson 61min), McCann, Boyd, Bostwick, Tomlin, Sinclair (sub Taylor 63min). Unused subs: Day, Newell, Knight-Percival, Clarke-Harris.
Leeds: Kenny, Peltier, Drury, Lees, Pearce, Austin, Becchio (sub Gray 86min), Varney, Norris, Diouf (sub Byram 75min), McCormack (sub Poleon 79min). Unused subs: Ashdown, Kisnorbo, White, Brown.
Attendance: 10,432 (3,701 Leeds fans)