Alex headed a late equaliser just moments after Mustapha Yatabare had given the hosts the lead in a 1-1 draw on Saturday in Ligue 1.
"We couldn't really develop our usual football on this pitch," Sirigu told the club's official website.
"We played a side that is used to playing here on this pitch. Guingamp looked to attack on the counterattack and with set pieces, which they are very good at.
"Coming back to equalise is very important and we were very professional."
PSG host Bordeaux at Parc des Princes in their next match on Friday.