Mousinho and Foster were shown straight red cards in last week's 2-0 defeat by Northampton and have been handed three and four-match bans respectively.
Meanwhile, striker Winn completes the three-game suspension he was given for his sending-off in the 1-0 loss at Southend on April 22.
Westley, who knows a win for his side will secure them a League Two play-off spot, admits his squad is stretched thin with the bans, but is strong enough to cope with the losses.
Midfielder Lawrie Wilson is expected to return from the knock which kept him out of the Cobblers match to give the squad a much-needed boost.
Source: PA
Source: PA