After 38-year-old Roma captain Francesco Totti cancelled out Sergio Aguero's early penalty with a goal that made him the oldest scorer in Champions League history, City had most of the play, but lacked ideas in attack.
The hosts had 59 percent of possession, but mustered only two shots on target to Roma's four, and might have finished on the losing side had goalkeeper Joe Hart not saved from Gervinho and Miralem Pjanic.
Roma now trail group leaders Bayern Munich by two points, with City three points further back ahead of a double-header against CSKA Moscow.
Pellegrini appeared to acknowledge that his side were being over-run in midfield when he sent on James Milner for Jesus Navas at half-time, but he said it was sloppiness, rather than tactical failings, that had hampered his team.
"Every time you don't reach the result you want, there's a lot of different things you could do," he told a press conference after Tuesday's game at the Etihad Stadium.
"But we were playing very well in the last games, so it was not an easy decision to change (the team) from the beginning
We play a lot of strong teams in this way and we do it very well.
"Today (Tuesday) we weren't very accurate with our passing and when we lost the ball, maybe we didnt have enough midfielders to cover.
"But I don't think that was the reason
The main problem was we lost many easy passes."
The hosts took the lead from practically their first attack, with Aguero scoring from the penalty spot in the fourth minute after he had been dragged back by former City right-back Maicon.
But Roma responded impressively, driving deep into City territory with pacy counter-attacks, and equalised in the 23rd minute when club talisman Totti deftly chipped Hart from Radja Nainggolan's through-ball.
While Roma had chances to extend their lead -- Hart saving from Gervinho and Pjanic either side of half-time -- City saw most of the ball in the second half, but without truly extending their opponents.
- 'We played with personality' -
Failure to win in Moscow on October 21 will leave the English champions at risk of a third group-stage exit in four seasons, but Pellegrini said there was no need to reach for the panic button just yet.
"We have only one point from (a possible) six, but we're only three points behind Rome," said the Chilean, whose side lost 1-0 to Bayern two weeks ago.
"It depends on a lot of things
We hope we can win the next game in Russia
We have 12 more points to fight for and we'll try to fight until the end to qualify."
Asked if Roma had produced the best performance of his year-old reign, visiting coach Rudi Garcia said: "I don't know, but what pleased me was that the team played with personality.
"The key word of the build-up was to play with confidence
We had everything to win and nothing to lose
We managed the game well.
"Taking a point allows us to stay three points ahead (of City) and enables us to approach the rest of the competition with confidence."
The Frenchman, whose side had won their six previous games in all competitions, said City's mid-game tactical switch was testament to Roma's impressive display.
"We equalised, then City changed their tactics," he said.
"It was a good sign for us, because it showed the other coach recognised the strain his team was under."
Garcia also gave short shrift to press reports linking his injured Dutch midfielder Kevin Strootman with a move to City's domestic rivals Manchester United.
"You'll have to ask the president," he said
"Luckily he's here, but I think my president has already answered that question."
Source : AFP
Source: AFP