Manchester City may have secured their passage into the FA Cup fifth round, but manager Pep Guardiola was left far from impressed by what he witnessed at the Etihad Stadium on Saturday. Despite a 2-0 victory over League Two outfit Salford City, the Catalan coach offered a scathing assessment of his side's display, labelling the performance "flat and slow and not good." It was a result that got the job done, but the manner of the victory left much to be desired for the reigning Premier League champions.The Blues found themselves ahead early on, but it wasn't through their own creative ingenuity. Instead, they were gifted an advantage in the sixth minute when Alfie Dorrington turned the ball into his own net to give the hosts a 1-0 lead. Rather than kicking on and dismantling their lower-league opposition, City retreated into a sluggish rhythm that frustrated the home crowd and clearly incensed their manager on the touchline. For long periods, the gulf in the footballing pyramid was barely visible as Salford held their own against the treble winners.In the build-up to the clash, Guardiola had been vocal about the relentless nature of the footballing calendar. City have effectively been playing two games a week for the entirety of the campaign, coupled with the immense psychological pressure of a neck-and-neck Premier League title race against the likes of Arsenal and Liverpool. However, when fronting the media after the final whistle, the City boss refused to hide behind the exhaustion of his players as a reason for the lacklustre showing.Guardiola was clinical in his post-match analysis, suggesting his players failed to grasp the tactical requirements of the game. "We didn't read the spaces where we were," he said. "The spaces in attack depend on how they defend and we didn't read it. We spent a lot of time to make the process a little quicker than that. The only good news [is] that we go through. That's all. It would be nice for me to say mentally we're exhausted, we're tired. It has been a tough two or three weeks for many reasons but it's our job. We have to do what we have to do. The calendar says to play every few days. We just didn't read where the spaces were and that's why everything was flat and slow and not good."With the game precariously balanced at 1-0 and Salford growing in confidence, Guardiola was forced to turn to his bench to inject some much-needed quality. It highlighted the importance of City's activity in the winter market, as heavy investment was required to see off the minnows. It wasn't until the 81st minute that the result was finally put beyond doubt, as Marc Guehi popped up to score the second and effectively end Salford's dreams of a historic upset.The struggle to break down League Two opposition will serve as a wake-up call for several first-team regulars who failed to seize their opportunity. While the statistics showed City dominated the ball, they lacked the incisiveness usually associated with a Guardiola team. The manager only found satisfaction in the final ten minutes of the contest. Once the second goal hit the back of the net, the tension evaporated, but the preceding 80 minutes had already left a sour taste in the manager's mouth.Despite the "boring" nature of the win, Manchester City's quest for silverware on multiple fronts remains active. The draw for the fifth round of the FA Cup is scheduled for Monday evening, taking place just before the cup tie between Macclesfield and Brentford. City will be keeping a close eye on the balls as they look to navigate a path back to Wembley, though they know they cannot afford many more performances of this substandard quality if they are to defend their crown.The schedule shows no signs of slowing down, with European commitments also looming large on the horizon. The Blues are currently waiting to discover their opponents for the Champions League last-16, which will be determined following the play-off matches between Inter and Bodo/Glimt, and Real Madrid and Benfica later this month. For Guardiola, the focus remains on finding consistency and ensuring his side recovers their tactical sharpness before the business end of the season truly kicks into gear.