Sergio Aguero is a doubt for Manchester City's Premier League clash against West Brom on Tuesday night.
The 32-year-old returned for City in last week's Champions League match against Marseille following weeks on the sidelines with an injury, but missed the Manchester Derby on Saturday.
Speaking ahead of the match, Guardiola said he will wait until Tuesday to decide whether or not to include the Argentine in his team.
“Today he was training. The last two or three days he could not train,” Guardiola revealed.
“Today he trained, and we will decide tomorrow.”
The Spaniard also revealed they will still miss the services of both Eric Garcia and Oleksandr Zinchenko due to injuries.
“Eric is still not fit, Oleks neither. The rest are OK,” added Pep.
Man City drew Borussia Monchengladbach in the Last 16 of the Champions League, and Guardiola knows it will not be a walk in the park.
“I learned when I was in Germany how big, important, and historical a team they are. I respect the beauty of their football,” Guardiola asserted.
“I saw highlights, not full games (and) to go through from the group with Shakhtar and Inter - made two incredible games against Shakhtar.
“All I can say is I want to arrive in the best possible condition when we play them. We will try and arrive in the best condition and best mood as possible. We want to compete as best as possible and go through.”
City are ninth in the English Premier League on 19 points, six off leaders Tottenham and Liverpool, who are tied on 25 each.