The Blues seemed set for another frustrating day at Stamford Bridge after Tammy Abraham saw his header hit the bar and Martin Dubravka denied Christian Pulisic.
But they finally got their reward for relentless second-half pressure when Spanish left-back Alonso drove in a firm, angled shot in the 73rd minute.
They should have scored a second through Abraham, but the England international’s shot was brilliantly blocked by DeAndre Yedlin.
Steve Bruce’s Magpies were preoccupied with defending for much of the match and failed to test Kepa Arrizabalaga.
Defeat means they drop into the relegation zone, although their manager will point to the fact they have now played every one of the ‘big six’ in their first nine games, bar Manchester City.
Relief for Lampard and Chelsea
Another match and another test passed by Blues manager Frank Lampard.
With only one clean-sheet in 12 games under his tenure, and only five points from their tally of 14 going into the game collected at Stamford Bridge, some had begun to question whether his side could handle the pressure at home.
In the first period the Blues looked off-colour and produced only a couple of half-chances, courtesy of Willian, while England midfielder Ross Barkley limped off injured just before the break.
But in the second half his side looked the embodiment of the spirit of the former Blues midfielder as they persistently tested Newcastle’s defence.
After Abraham’s header came off the bar and Dubravka had pulled off a wonder-save, they finally made the breakthrough when Alonso found the keeper’s bottom left.
It was relief as much as celebration around the ground. The home side should have settled their fans’ nerves moments later but Abraham was denied by an excellent stop from Yedlin.
Saint-Maximin shines again
Newcastle are in the bottom three, but this display suggests it is not time to panic just yet.
Once again the Magpies shone defensively, with Dubravka, Yedlin, Fabian Schar and Ciaran Clark leaving everything on the pitch. And perhaps against weaker opposition the effervescent Allan Saint-Maximin will have seen some of his lung-bursting runs have an end result.
The Frenchman is a new fans’ favourite on Tyneside and looked most likely to either score for his team or provide an assist. Unfortunately for him and the travelling support, record signing Joelinton was not on the same wavelength in attack.
Bruce threw on forwards Andy Carroll and Dwight Gayle in the last 20 minutes but they failed to make an impact.
Man of the match – Tammy Abraham
‘We want more’ – reaction
Chelsea manager Frank Lampard: “The second half was the most pleasing thing. It was a good test for us today. We changed things a little in the second half and we showed a little more flexibility and creativity.
“We were upbeat, we had urgency, the tempo was good, and that got us the win.
“We want to score goals. You can see the fans – I think they’re happy with what they’re seeing at the moment. We want more.
“If we want to keep moving up, we can do better. So far this season, though, things are going well.”
On Ross Barkley’s injury:“It’s an ankle injury. We need to assess it and see how bad it is.”
Newcastle head coach Steve Bruce: “We had a few chances in the first half in particular, but we didn’t pick the right pass or the right cross.
“Chelsea have a nice blend of youth and experience at the moment. We didn’t weather the storm in the second half.
“We’ve had a really tough start. We’ve now got a run of games against teams who are going to be in and around us. Hopefully we can get a few points.”
Defender Alonso most predatory – the stats
- Chelsea have won more Premier League home matches versus Newcastle than they have against any other team (18).
- Newcastle have won just one of their past 26 away league games against Chelsea (D7 L18), losing the last seven in a row.
- Chelsea have won eight consecutive games against Newcastle at Stamford Bridge in all competitions for the first time since December 2007, with six different managers taking charge of these wins.
- Newcastle have lost three consecutive away Premier League games for the first time since May 2018.
- Bruce has won just one of his 22 Premier League matches against Chelsea as manager (D5 L16), losing each of the last seven in a row.
- Since the start of the 2016-17 season, Alonso has scored more Premier League goals than any other defender (16).
- Chelsea named five English players in their starting XI for a Premier League match (Fikayo Tomori, Barkley, Mason Mount, Callum Hudson-Odoi, Abraham) for the first time since February 2013, which was also against Newcastle.
- Hudson-Odoi became the first teenager to create five or more chances in a Premier League game for Chelsea since Romelu Lukaku v Blackburn in May 2012.