The attacking marquee was in devastating form during Brisbane's 3-1 victory over Perth Glory last week that gave the two-time champion a seven-point lead over Western Sydney Wanderers at the top of the table with six rounds to go.
As Brisbane prepares to host third-placed Adelaide United in a Suncorp showdown on Sunday, Smith said he could not speak highly enough of Broich's massive contribution to the team.
"Thomas Broich is the best player in the A-League," Smith said.
"He is the best marquee player and we are very privileged to have had him in Brisbane for four seasons.
"We always work on our structure and make sure everyone plays well within that structure.
"But Thomas is our X-factor. He is our star who is driven, who can create something from nothing and who can score goals.
"When the team performs well around Thomas he then goes to a next level.
"He sees things that other players can't see and when he's in form he gives us all a boost.
"With the position that he plays as one of the front three, if he hits top form in the later stages of the premiership and in the finals, he could win us the championship. Definitely."
Smith said he was pleased to note that Brisbane's refusal to lose faith in its ability when it was going through a rough patch was vindicated by its polished performance against Perth.
"We were not at our best but we put in a good display," he said.
"We never lost the belief and always had confidence in our ability.
"We have some fantastic players in the team but we did not perform to our potential against Melbourne heat and Newcastle Jets and we lost both games.
"We worked very hard at training "¦ and okay I know games are different "¦ because we knew that if we stuck with our structure and played with discipline we would return to the form expected of us."
Brisbane has a tough nut to crack against Adelaide on Sunday but it could turn into a rewarding day.
Depending on the result of Saturday's derby between Sydney FC and the Wanderers, Brisbane could be playing for a 10-point lead with five rounds to go.
Smith however said that increasing the seven-point gap on the Wanderers was not a priority as far as he was concerned.
"Our main focus is improving on the benchmark we set last week," Smith said.
"We want to put in a better performance than we did against Perth ... we never focus on points or gaps "¦ what we want to do is peak at the right time of the season.
"Our whole pre-season and conditioning was aimed at us peaking at this point of the season."
Adelaide has received plenty of plaudits for its cultured football that took a while to gell but it is beginning to bear fruit.
Adelaide's modern game based on movement and passing is similar to Brisbane's and the match at Suncorp that should draw a healthy crowd could turn into a 'playoff' for bragging rights after the teams won one of their two clashes this season.
"To be completely honest, I'm very pleased that Adelaide are playing the type of football they are playing because it shows how far the league has come," Smith said.
"Adelaide can play a very entertaining brand of football.
"In terms of bragging rights, I won't go into the game thinking we have to put one over Adelaide because we are both playing positive football.
"We set benchmarks against our own performances. I don't compare our team with other teams."