Smith was instrumental in leading the Highlanders to a 24-14 playoff win over the Chiefs at Forsyth Barr Stadium.
Former All Black halfback Justin Marshall said Smith was back playing to his high standard and had been the catalyst for the Highlanders' performances over the second half of the season.
''I thought he had a fabulous game and was getting back to his high standards he had set in previous seasons,'' Marshall said.
''In the first half of the season, he was still playing well but looked as though he was playing within himself. But the last half of the season, he has been the catalyst of the Highlanders going so well.
Marshall, who played 81 tests, said Smith's running game was important not only to the Highlanders but also the All Blacks.
''He showed how good his running game can be in the weekend. His running game made the game for the Highlanders.
''He looks excited about his rugby. Maybe earlier in the year he was looking a bit tired ... but at the level he was playing on Saturday night, it was just great to be there.''
Marshall said he noticed Smith was out warming up very early and he used that energy and passion right through Saturday night's game.
Marshall believes Smith's form could be attributed to pressure being put on his position by Hurricanes halfback TJ Perenara.
''There is no doubt he is the unequivocal No 1 but it is always good to have pressure on. I know when I was playing, it was good internal motivation to keep you playing at your best.''
Former All Black and Otago halfback Chris Laidlaw said Smith's display was absolutely flawless.
''That was the best display of rugby I have ever seen from a halfback,'' Laidlaw said.
''I would regard him as the one person who they [All Blacks] can not do without. To me it is him and [Brodie] Retallick who are indispensable.
''If he is not the greatest halfback we have had now, then he will be very shortly.''