It had been 195 days since City announced Guardiola would succeed Manuel Pellegrini at Etihad Stadium, and results stagnated during that period, with five wins from last season’s final 15 Premier League games leading to a fourth-placed finish.
Guardiola, 45, arrived in Manchester with six league championships to his name – three each from his spells at Barcelona and Bayern Munich – and brings an expectation he will guide City to a first Premier League title since 2014.
But any hopes of an instant revolution were curtailed by a lethargic performance that lacked creative spark, despite dominating possession against a side that only avoided relegation in their penultimate game last season.
And, while City may have required good fortune for the decisive goal – McNair heading in Jesus Navas’ cross at the back post, it provides a winning platform for Guardiola, who was lacking injured first-team players Vincent Kompany, Samir Nasri, Nicolas Otamendi and new signings Leroy Sane and Ilkay Gundogan.
Guardiola shows Hart-less streak
Hart’s absence from the starting line-up is the most eye-catching decision of Guardiola’s early days at City, and will raise the question whether the 29-year-old’s 10-year stay at Etihad Stadium could be coming to an end.
The former Shrewsbury player has made 347 appearances for City, winning two Premier League titles, an FA Cup, two League Cups and 63 England caps, but Guardiola opted to start with Willy Caballero.
The Argentine made a notable stop from a point-blank Defoe effort, before the striker slid home a cool finish.
Midfielder Yaya Toure was left out of the squad altogether, but the influential Ivorian may have been saved for Tuesday’s first leg of the Champions League qualifier at Steaua Bucharest.
John Stones, a £47.5m summer signing from Everton, looked composed at the heart of City’s defence alongside Aleksandar Kolarov, and fellow debutant Nolito put in an enthusiastic performance on the wing.
Sunderland can take encouragement
Sunderland’s preparations for the new season were torn apart by manager Sam Allardyce’s decision to leave for the vacant England job, but his departure opened the door for Moyes’ return to the Premier League.
The Scot’s reputation was knocked by a difficult year as Manchester United boss, followed by an equally chastening 12 months at Real Sociedad.
But he could well be liberated by the shift in pressure from replacing the legendary Sir Alex Ferguson at Old Trafford to starting out at a club looking to improve on last season’s 17th-placed finish.
Three of Moyes’ four summer signings featured, Donald Love starting at right-back, and Adnan Januzaj and McNair coming off the bench, but the latter’s debut will be remembered for the own goal he scored just three minutes and 35 seconds after coming on.
Despite rarely seeing the ball, Sunderland restricted the hosts’ chances and will be buoyed by the quality of their goal – Defoe scoring in his 16th Premier League season by slotting home from a Jack Rodwell through-ball.
Man of the match – Fernandinho
What they said
Manchester City boss Pep Guardiola: “It was tough for everybody and that is why people say the Premier League is tough. We were constant and we deserved the victory.
“All of the new signings were a team so we fight. We spoke many times what we should do like a team – this is just the first step.
“But, of course, for the new people, new manager, new players to start winning helps to believe in what we are doing.”
Sunderland boss David Moyes: “You couldn’t deny that City were the better team because of the players and the football they played but we did everything we could to make their football difficult for them.
“For long periods we did a great job at it, but it is disappointing that we gave away the second goal.
“But I can’t be critical of the players because they did a great job defensively and all-round really – just disappointed we didn’t get a point.”
Manchester City travel to Romania on Tuesday for the first leg of their Champions League qualifier against Steaua Bucharest, before going to Stoke in the league on Saturday. Sunderland host promoted Middlesbrough on Sunday, 21 August.
The stats you need to know
City have won their past five Premier League meetings with Sunderland.
Sunderland have never won at City in the Premier League (W0 D2 L11).
Aguero is the top-scoring player in the Premier League so far in 2016 (18 goals in 19 games).
Guardiola has won the opening league game of the season as a manager in each of his past seven seasons (three for Barcelona, three for Bayern, one for City).
Only Alan Shearer (11) has scored more Premier League goals against City than Defoe (eight – level with Wayne Rooney, Robbie Keane and Ian Rush).
McNair was the first player to score an own goal on his Premier League debut for a team since Danny Gabbidon for QPR exactly five years ago
Match ends, Manchester City 2, Sunderland 1.
Second Half ends, Manchester City 2, Sunderland 1.
Corner, Sunderland. Conceded by Fernandinho.
Foul by Fabian Delph (Manchester City).
Wahbi Khazri (Sunderland) wins a free kick on the left wing.
Fernandinho (Manchester City) wins a free kick in the defensive half.
Foul by Adnan Januzaj (Sunderland).
Aleksandar Kolarov (Manchester City) is shown the yellow card for a bad foul.
Foul by Aleksandar Kolarov (Manchester City).
Adnan Januzaj (Sunderland) wins a free kick in the defensive half.
Corner, Manchester City. Conceded by Donald Love.
Attempt blocked. Kelechi Iheanacho (Manchester City) left footed shot from the centre of the box is blocked. Assisted by Sergio Agüero.
Foul by Kelechi Iheanacho (Manchester City).
Younes Kaboul (Sunderland) wins a free kick on the left wing.
Own Goal by Paddy McNair, Sunderland. Manchester City 2, Sunderland 1.
Attempt blocked. Kelechi Iheanacho (Manchester City) left footed shot from outside the box is blocked. Assisted by Jesús Navas.