Johnson, newly signed at £17million, came on as a second-half substitute in an unfamiliar left-back position, Liverpool boss Rafael Benitez having limited options on that flank following the knee injury to Fabio Aurelio.
But Johnson almost scored within minutes of coming on, racing up on the left to fire across goal. And then he appeared on the right flank to create a great chance, spurned by Lucas.
Benitez played two entirely different sides in each half, and Yossi Benayoun also impressed, almost winning the game with a swerving shot beaten away by keeper Reto Bolli in the final seconds.
Youngster Dani Pacheco had twice wasted good opportunities, but St Gallen had the best openings.
Mario Caceres hit a post in the first half, while veteran striker Mario Frick planted an unopposed header wide from eight yards out in the second period.
Liverpool were without their Spanish contingent, as well as Javier Mascherano.
The build-up to this warm-up tour has been dominated by the possible transfer of Xabi Alonso to Real Madrid.
The Spanish club will try to complete a deal before the weekend, but they are still believed to be unwilling to pay the £30m asking price.
Former Liverpool goalkeeper Jerzy Dudek, now at Real, summed up his club's desire earlier in the day at the club's Dublin training camp by saying: "Of course we want good players, and Xabi is a very good player. I hope he joins us, we certainly all want that."
Benitez was confronted with "Don't let Xabi go" banners from Liverpool fans during this match, and he is clearly not prepared to be bullied over the issue by the Spaniards.
His immediate concern was getting pre-season off to a good start.
Liverpool began this friendly in the AFG Arena with just skipper Steven Gerrard and defender Jamie Carragher in the starting line-up who would expect to be on the pitch for the Premier League opener next month.
But it gave the chance for long-term injury victim Phillip Degen to make his comeback in his homeland, while striker Andriy Voronin started up front.
The Ukrainian had a successful loan spell with Hertha Berlin last season and has returned to the squad intent on proving he can salvage his Anfield career.
And he started well, linking with Gerrard and working constantly behind Hungarian youngster Krisztian Nemeth.
The 20-year-old saw a first-half shot scrambled away by keeper Bolli, while Gerrard went close from long range.
Liverpool used three goalkeepers during the game - Diego Cavalieri, David Martin and Peter Galacsi - and none of them had a shot to save.
But at the other end the Reds were unable to turn their greater possession into goals.
They are next in action on Sunday against Rapid Vienna in the Austrian capital, by which time the future of Alonso should be much clearer.