City make the trip to Portugal looking for a response after suffering back-to-back away defeats to Tottenham Hotspur and Bournemouth in the EFL Cup and Premier League respectively.
Guardiola has already acknowledged that the top-flight champions were nearing being down to the bare bones of the squad for the trip to the Vitality Stadium at the weekend.
On a more positive note for City, they sit in third place in the Champions League table after three games, putting them in a favourable position to finish in the top eight.
Nevertheless, Guardiola continues to deal with widespread issues ahead of facing opponents in Sporting who have also accumulated seven points from their opening three fixtures.
Which Man City players missed training?
As per the Manchester Evening News, there were five players who were not seen during training on Monday morning.
Rodri and Oscar Bobb are already known to be out in the long term with a serious knee injury and a fractured leg.
Each of John Stones, Ruben Dias and Jack Grealish also played no part in the session and are seemingly not in contention to travel with the squad to Portugal.
Guardiola had already indicated that neither of Stones or Dias would feature against Sporting, whose head coach Ruben Amorim will soon be taking over Manchester United.
Furthermore, Grealish falls into the same bracket in terms of injury recovery, it highly unlikely that he will play before the international break.
Better news for City
Kyle Walker surprisingly started and completed 90 minutes against Bournemouth, despite the suggestion that he would remain out with a knee issue.
Kevin De Bruyne was back on the substitutes' bench for the first time in more than six weeks, although the veteran playmaker was not risked in the second half.
However, both of the veterans featured in training on Monday, even though Guardiola may err on the side of caution when it comes to risking them.
In both cases, the Spaniard may feel that neither player should start - for differing reasons - when City have a two-week break after Saturday's Premier League meeting at Brighton & Hove Albion.