All three teams conceded at most just over 0.6 goals per game.
Nelson Oliveira, Ricardo Carvalho and Adrian Lopez would be ambitious targets.
Ricardo Carvalho has put pen to paper on a new one-year deal with AS Monaco, having been with the Ligue 1 club since 2013.
The latest Manchester United transfer news, views and rumours.
Manchester United are reportedly interested in signing former Chelsea defender Ricardo Carvalho.
Nathan Ake was revealed to be wearing the number six shirt this season, giving him hope for a key first-team role.
Chelsea legend Ricardo Carvalho believes there is no striker better in the world than Monaco teammate Radamel Falcao.
Javier Pastore gave PSG the lead, but a second half deflected goal by Fabinho gave Monaco a share of the points.
Ricardo Carvalho was in a rush to get back into the action in his side's 1-1 draw with Montpellier.
As another Chelsea connection arrives in the principality we look at the comparisons between the two clubs.