Ross Wallace forced Marshall into a save on the half-hour mark when he cut in from the right and let fly from range.
However, Wednesday's task of getting back into the game was only made more difficult when Anthony Pilkington raced on to a long ball before rounding Westwood and rolling into an empty net as the visitors pushed men forward in search of the equaliser.
Kenwyne Jones thought he had made it 3-0 towards the end of the half but his header was flagged offside after Westwood had denied Watt with an excellent save.
Wallace's corner found Glenn Loovens before the hour mark, but Marshall was well placed to deny the Wednesday centre-back.
Noone came close to adding to his tally for the afternoon with a 25-yard effort, but the arrears were halved moments later through Forestieri.
The former Watford man was allowed time and space to let fly from around 20 yards, and the effort beat Marshall, and Wednesday's comeback was complete on 76 minutes when Barry Bannan scored his first goal for over two years.
Neither side were able to force a late winner as the spoils were eventually shared at the Caridff City Stadium.