Last weekend's shock opening-day loss at home to Burnley – a match where captain Gary Cahill and Cesc Fabregas were sent off – and the ongoing saga over Diego Costa's future has cast an unwelcome shadow over Stamford Bridge and sounded unwelcome echoes of the last campaign they entered as champions.
Jose Mourinho paid with his job before Christmas in 2015 as a squad in turmoil hovered improbably over the relegation zone but Antonio Conte's side allayed doubts over a similar implosion as they turned in a performance of grit and togetherness at the national stadium.
Alonso produced the champagne moment in the 24th minute and a remodelled defence, featuring Andreas Christensen on his first Premier League start, repelled waves of Tottenham attacks with increasing ease until a striker undid their good work.
It left Alonso to step up thrillingly once more. The wing-back stormed into the Spurs box to catch out Hugo Lloris at the near post two minutes from time, leaving Conte to unfurl trademark touchline delirium.
Chelsea's injury and suspension issues meant Tiemoue Bakayoko was forced an ahead-of-schedule debut in midfield, where David Luiz was employed in a holding role.
Nevertheless, Conte's men started impressively and should have led in the fifth minute when Alvaro Morata wastefully headed Cesar Azpilicueta's cross wide from close range.
Harry Kane forced Thibaut Courtois into an unconvincing 10th-minute save with a low, dipping drive, while Dele Alli smashed over from an acute angle when Christensen misjudged Toby Alderweireld's raking ball forward.
However, it was Chelsea who drew first blood in the 24th minute after Alli fouled Luiz 25 yards from goal.
Willian, who netted a free-kick in Chelsea's 4-2 win over Spurs on the same ground in last season's FA Cup semi-final, stood over the ball but Alonso stepped up to curl a sumptuous strike into the top corner.
Kane took it upon himself to drive the Spurs response – muscling past Chelsea's goalscorer to draw a block from Courtois before pulling an effort wide on the next attack before the half hour.
He went closer still in the 42nd minute when, following a driving run from Alli, he fired against the base of the post. The England striker will wonder how the anomaly of him failing to register a Premier League goal in August remains.
Spurs full-back Ben Davies then had a deflected strike pushed behind, Courtois ensuring the champions' advantage remained at the interval.
Kane's header from an early second-half corner was blocked by Luiz and Pochettino's side peppered the Chelsea box with set pieces to no avail as the game ticked past the hour.
With 20 minutes to play, Willian instigated a counter-attack that ended with Morata's shot spinning wide off the prone Alderweireld.
The Brazilian impressed in a roving attacking role behind Morata and it was his turn to test the upright in the 74th minute, his low strike fizzing past Lloris' despairing dive and cannoning to safety.
Conte's side looked set to rue those misses when Batshuayi badly misjudged Christian Eriksen's free-kick but Alonso resoundingly answered any brewing questions over their team-spirit, meaning further Wembley heartache for Tottenham.
Key Opta Facts:
- Spurs' 19-game home Premier League unbeaten run has come to an end, with Chelsea the first side to beat Spurs away from home since Southampton in May 2016.
- Tottenham have lost seven of their last nine matches at Wembley (W1 D1) and lost each of their last four games against Chelsea there.
- Harry Kane had eight shots, his most in a Premier League game without finding the net. Kane has now had 34 shots and played 12 games in the month of August without scoring in the Premier League.
- Marcos Alonso has scored two direct free-kicks in the Premier League since the start of last season, with only Philippe Coutinho (3) scoring more.
- Since the start of last season, no Chelsea player has scored more Premier League braces than Alonso (2, level with Diego Costa and Eden Hazard).
- Michy Batshuayi was the first substitute to score an own-goal for Chelsea in the Premier League since Michael Duberry against Leicester City in April 1999.
- The last four goals Spurs have conceded from outside the box in all competitions have all been scored by Chelsea.
- Chelsea have never lost when they’ve been leading at half-time under Antonio Conte in the Premier League (W20 D2).