London - Manchester City coped admirably when leading striker Sergio Aguero was on the treatment table earlier this season but take midfield powerhouse Yaya Toure out of the engine room and the machine starts grinding to a halt.
After a sluggish start to the season Ivory Coast's Toure was at his marauding best in the final weeks of 2014, scoring six goals in eight games as champions City closed an eight-point gap to Chelsea in the Premier League.
Since he departed for the African Cup of Nations, however, City have lost momentum, drawing 1-1 with Everton last week and on Sunday losing 2-0 at home to Arsenal -- a defeat that left Manuel Pellegrini's team five points behind Chelsea.
In fact, of the four Premier League games the 31-year-old Toure has missed this season, City have won none of them.
They may have a squad laden with household names, but when he is in the mood it is Toure who still makes them tick, still the go-to man when trouble is brewing.
Arsenal's first win at The Etihad since 2010 was built on stifling City's midfield creativity and hitting the hosts on the break. When chasing the game after falling behind to Santi Cazorla's first-half penalty, City badly missed the sledgehammer power Toure provides with his runs and his shooting.
With a trip to Chelsea in their next league match on Jan. 31, Pellegrini can only hope Toure is not detained too long in Equatorial Guinea, although it would be a major surprise if he was back in time for the clash at Stamford Bridge.
"We didn't play a very good game. We ran a lot, we had a lot of possession, but we didn't have creative ideas to try to find the space against a team that defended very well," Pellegrini told reporters. "We conceded two goals from set pieces.
"Yaya Toure is a very important player for us, but we played without Sergio Aguero and now we must play without Yaya. This team cannot depend on just one player.
"That is not the reason why we lost."
Pellegrini said his side must now win at Chelsea to repair the damage done by Sunday's tepid display.
"The game at Stamford Bridge is a very important game. We must close the gap to two points," he said.
"I hope that we are going to recover and play in the way we have so far, except for this game."