Arsenal took the lead early on as Gabriel Martinelli headed home in the fifth minute, but the Gunners suffered an injury blow as winger Bukayo Saka limped off in the first half. His replacement, Reiss Nelson, bagged two goals early in the second half before Thomas Partey's rocket made it 4-0 inside an hour. Martin Odegaard then put some gloss on the scoreline in the 78th minute.
ESPN has reaction and analysis from Emirates Stadium.
1. Nelson stakes his claim to help replace injured Saka
Saka began the game in outstanding form, proving a constant threat on the right side, but the England winger landed awkwardly under a rough challenge from Forest left-back Renan Lodi on 17 minutes that caused him to limp to the touchline. It looked for a moment like it may have just been a scare, but he went down again shortly after, and a member of the Arsenal medical team walked over to manager Mikel Arteta to inform him Saka needed to be substituted.
The England international, who will be looking ahead to next month's World Cup, has played a lot of football this season. He has started in all but one of Arsenal's 11 previous Premier League games this season, as well as making appearances in all five Europa League ties, with his creativity and dynamism one of the pillars upon which Arteta's turnaround has been built. And so Arteta's choice of replacement was significant.
Nelson, who hadn't played a minute in the Premier League this season, got the nod -- ahead of Brazilian teenager Marquinhos and €35 million summer signing Fabio Vieira -- and he delivered in style. Nelson stole the show in the second half with a well-taken first goal before adding a second moments later as he arrived at the right time to prod home a cross from Gabriel Jesus. It was an interesting choice of replacement, given the 22-year-old's recent spells on loan at Hoffenheim and Feyenoord, but one that paid off.
It is unclear the extent of Saka's injury, but should he miss any length of time, Arsenal will need Nelson to continue to provide more performances like he did in the second half.
2. Arsenal 'reset' in style after PSV collapse
Arteta looked a little dejected after the midweek defeat at PSV in the Europa League and spoke of needing a "reset." The Gunners had edged their way to three wins against Bodo/Glimt, Leeds United and PSV, then slumped to a rare 1-1 draw against Southampton before collapsing 2-0 against PSV in the return game.
So facing a Forest side still buzzing from an upset win over Liverpool, it was time for Arsenal to show the newfound mentality their players have spoken of all season. And it took just a handful of minutes to display just that.
Arteta's side were ahead within five minutes as Martinelli headed in a superb delivery from Saka. The quick-fire second-half double from Nelson essentially put the game to bed before midfielder Partey got in on the action with a superb strike from the edge of the box. Arsenal scored a fifth through a left-footed rocket from Odegaard on 78 minutes.
In truth, Arsenal never looked troubled in defence, and their attacking efforts were much more clinical than in weeks past. The reset Arteta requested was duly delivered.
A comfortable win over Forest could be seen as much-needed respite for a side that had begun to look a tad jaded. Next they must polish off their Europa League group with a win over FC Zurich, and then face Chelsea and Wolves in their final two Premier League games before the World Cup. Wins there would mean Arsenal go into the break at the top of the table and ensure their stellar start to the season remains firmly intact.
If they have hopes of a title challenge, staying ahead of Manchester City as much as possible over the coming months will be key.
3. Forest need to fix away form ... and goals
Forest's record transfer spending and torrid Premier League form provide stark viewing. The newly promoted side signed a whopping 23 players this summer with over £150m in spending, but it has not gone to plan. A dismal run has left them at the bottom of the table with just two wins -- over West Ham in August and against Liverpool last weekend.
Maybe it is tough to judge Forest in games against Liverpool and Arsenal where they were always expected to struggle, but the nature of Sunday's 5-0 defeat will worry manager Steve Cooper. A late goal from Brennan Johnson against Everton stands as their only away goal so far this season. The City Ground has not been much of a fortress, either.
It paints a grim picture. The fact the club sacked head of recruitment George Syrianos and head of scouting Andy Scott earlier this month points to a summer of regret, and that was laid bare at the Emirates as two of their big-name arrivals from that period -- Jesse Lingard and Morgan Gibbs-White -- put in pedestrian performances.
That must now be put in the past: The squad is what they have until January at least, and they must get back on the path to survival.
Arsenal: Ramsdale 6, Gabriel 7, Saliba 7, Tomiyasu 7, White 7, Partey 8, Xhaka 8, Odegaard 8, Gabriel Jesus 8, Gabriel Martinelli 7, Saka 7.
Subs: Nelson 9, Tierney N/A, Nketiah N/A, Soares N/A, Viera N/A.
Forest: Henderson 6, McKenna 5, Cook 5, Lodi 6, Aurier 5, Freuler 6, Kouyate 6, Yates 6, Awoniyi 5, Lingard 5, Gibbs-White 5.
Subs: Johnson 6, Dennis 6, Worrall N/A, O'Brien N/A, Williams N/A.
Best and worst performers
BEST: Reiss Nelson
Despite his small stature, Saka's exit on 27 minutes left big boots to fill, and Nelson passed the test with flying colours. It was his first Premier League appearance this season, and the 22-year-old could prove to be a worthwhile understudy should Saka miss time.
WORST: Jesse Lingard
The former England international did very little in what could have been the kind of counterattacking game where he usually thrives. Manager Steve Cooper subbed him off after 56 minutes, and he was not missed.
Highlights and notable moments
Arsenal took the lead through Martinelli's header.
Arsenal wasting NO time.— NBC Sports EDGE Betting (@NBCSportsBet) October 30, 2022
Gabriel Martinelli was +470 to put the first one home.
Then Saka went off injured, which had England and Arsenal fans holding their breath.
Saka has come off in an apparent injury against Nottingham Forest 🤕— ESPN FC (@ESPNFC) October 30, 2022
The World Cup is less than a month away. pic.twitter.com/Ut1REEqXj1
Substitute Nelson made his case for more minutes with two goals.
Partey and Odegaard then struck two wonderful efforts home to make things safe.
After the match: What the players and managers said
Nelson: "It was amazing you know, we had a bit of a slow start after the goal but everyone got into the game and it was great to play in. Couldn't have gone much better than that for me after coming on. Delighted with the goals and the assist. I have been training for my chance and I got it and tried my best to take it."
On Saka's injury, he added: "Of course, it is a huge shame for Arsenal and the nation and we will go and check now and see how he is. He's a great boy and it's great to have him in the team. We are just trying to do well for the gaffer and the team. We're top now and it's nice, hopefully we can go all the way."
Arsenal manager Arteta on Saka potentially missing the World Cup: "Hopefully not. It was a bad kick, he was limping but I don't see it further than that. Both foot and ankle, he got kicked a few times."
On Nelson: "All his teammates and the staff are so happy for him, because he's a kid where he is really changing, evolving and maturing. He is showing every day how much he wants it. Today he had an opportunity, and he did extremely well because he helped us to win the game."
Forest manager Steve Cooper: "We don't just have to take it on the chin, we have to deal with it. We fell short today. Of course we could have played really well there and not got anything out of the game, it's a tough game, but in any professional sport the minimum is to be accounted and fight and be hard to be, and we just didn't do that well enough at the start of the game.
"I thought we settled okay... we had some moments were we looked a bit of a threat, and the second half was about continuing that with Arsenal chasing a second goal, maybe we could hit them on a breakaway, but the start of the second half we were nowhere near competitive enough. I can't think of tackles, even fouls, that can happen when you're competing. Players running past us, one-twos etc., in the end if you're not going to do that at this level then you're going to get hurt."
Key stats (via ESPN Stats & Info)
- Coming into Sunday, Arsenal, Manchester City and Lens were the only teams that have won each of their league home games in Europe's top five leagues.
- Arsenal were looking to start the Premier League season with six home wins for the first time since 2017-18, when they won the first seven home games of the season.
- Martinelli scored his fifth goal of the season in his 12th game. He scored six goals in 29 appearances last season.
- Arsenal have allowed just three first-half goals this season. Only Newcastle, PSG, Rennes, Atalanta and Lazio have allowed fewer in Europe's top five leagues this season (two each).
- Nelson scored his first Premier League goal since July 15, 2020 (vs. Liverpool). And then got another shortly after.
- Nelson scored his second career club-level brace and first since October 2018 with Hoffenheim (on loan) in the Bundesliga.
- Forest have scored just one goal in their seven away games so far, conceding 19.
- Gabriel Jesus may not have scored today, but he has assisted on 13 goals in the Premier League since the start of last season, ranking third behind Kevin De Bruyne (17) and Mohamed Salah (16).
Arsenal: The Gunners head to Chelsea next Sunday at 7 a.m. ET. They host Brighton in the EFL Cup in midweek, then their final game before the World Cup is against 19th-placed Wolves on Nov. 12 at 2.45 p.m. ET.
Nottingham Forest: After a couple of tough away trips, Forest are at home for their next three games. They face Brentford and Crystal Palace next in the Premier League and host Tottenham in the EFL Cup in between.