A late rally had the New Zealand side in with a chance of snatching a late win but the clock ran out on them.
"We probably should've and could've won," Matthews said.
"They were absolutely on their knees at the end of the game and if it had gone on a few more minutes I think we would've won.
"For most of the game we defended really well but against those type of sides you need to do it for 80 minutes."
Of the Wanganui quartet, Matthews said Tofa was strong in defence along with Rowe.
"Peter was just his usual self, made tackle after tackle."
Waitokia hurt his knee early on which hampered his movement.
Matthews said he tour would go down as an overall success with two wins against Nadi and NZ Marist.
"We played three in six days. Two wins out of three and we got close in the last games. It's about the performance as much as winning and losing," he said.
"They really did New Zealand proud of the field as much as on it."
Nadroga 26
NZ Heartland XV 22 ( Siua Moala, Kieran Coll, Willie Paia'aua tries, James Lash 2 con, pen)