The Argentina international has led by example, and not just in terms of goals, after Barcelona appeared to lose their sparkle in defeat at Atletico Madrid and draws away to VfB Stuttgart and Almeria over the last month.
"The first to promote the spirit of the team is Messi himself," Barca president Joan Laporta said after the 22-year-old forward scored twice in the 4-0 win over Stuttgart that put them in the Champions League quarter-finals on Wednesday.
Guardiola agreed that his importance to the team was not just about putting the ball in the back of the net.
"He is the first to pressure opponents, to try and win the ball back, to fight for every ball. His commitment is contagious for the rest of the team," he said.
The champions return to the domestic title race on Sunday at struggling Real Zaragoza (2000 GMT), and they will be looking for their first away win in four attempts in all competitions.
Barca have slipped back to second on goal difference behind leaders Real Madrid, and will be hoping Zlatan Ibrahimovic, Thierry Henry and Bojan Krkic step forward to try and share some of Messi's goal-scoring burden.
Zaragoza, 17th, are fighting hard to avoid a swift return to the second division and have only lost once in their last seven matches.
"We are playing a footballing giant, but we can be a little David and we can bring them down," Zaragoza's Brazilian midfielder Edmilson said of his former club, adding more cautiously: "A point against this Barca would feel like victory."
DIFFERENT COMPETITION
Real proved that their painful exit from the Champions League had only sharpened their hunger for the one remaining trophy available to them with a 4-1 hammering of Real Valladolid last weekend.
They host 12th-placed Sporting Gijon on Saturday having won all 13 league games at the Bernabeu this season.
The battle for Spain's other two Champions League qualification slots is almost like a separate competition.
Third-placed Valencia are a distant 18 points behind the leaders, and fourth-placed Sevilla 21 adrift.
Sevilla visit Espanyol on Saturday needing to lift themselves after their surprise exit from the Champions League at the hands of CSKA Moscow during the week. Valencia host improving Almeria on Sunday.
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