But the young Belgian put all his frustration behind him as he scored the goal that won the title for the Blues.
The 23-year-old, who had not started a single game in the league and was making his 18th substitute appearance of the campaign, pounced with just seven minutes left at the Hawthorns to score from close range.
The goal gave Chelsea the three points they needed for their fifth title under the ownership of Roman Abramovich – and a first in his debut season in English football for manager Antonio Conte.
For long spells last night it had looked set to be a frustrating evening for the Stamford Bridge club as chances were made and missed. Until the boy from the shadows struck.
Conte’s mantra all season long has been “hard work” – and that 10 months of graft culminated in a drizzly night in the Black Country.
Albion had nothing to play for but teams managed by Tony Pulis rarely roll over for anyone, so an easy evening was far from guaranteed. On the other hand, Conte’s team had won a dozen times on the road this season.
Chelsea were once again without Footballer of the Year N’Golo Kante, still struggling with a thigh niggle, so Cesc Fabregas, after an excellent performance against Middlesbrough on Monday, kept his place.
The prize was so near, yet so far. For the 2,700 Chelsea fans packed into the ground there was no doubt. They were raucous and lively.
Albion showed their intent after just a minute, when Salomon Rondon’s looping header had to be tipped over the bar by Thibaut Courtois. But Chelsea soon settled into their familiar, ominous rhythm and, when Fabregas set up Pedro from his free-kick, his shot was deflected an inch wide.
Ben Foster then saved from Cesar Azpilicueta’s low drive and Albion could barely get out of their half at times.
Fabregas took matters into his own hands as he advanced to the edge of the area and drilled a low shot just wide. Pedro then fired past the post when he should have done better. Diego Costa, up until then quiet, turned his marker but blazed over.
The Hawthorns had not been a particularly happy hunting ground for the Londoners, who had won only one of their previous five visits there. But it seemed as though a goal must come.
Victor Moses almost provided it with a low snap shot that Foster plunged to tip round the post, and then Craig Dawson almost put the ball into his own net.
Costa, though, was having one of those nights when his touch was awry, his runs unrewarded. The frustration was beginning to mount.
Fabregas was running the show from midfield for Chelsea – but for once there was no end product. Eden Hazard was quiet, Pedro running into blind alleys too often. And Albion suddenly began to believe – as Rondon almost caught the Chelsea defence out with a run from his own half, only stopped by David Luiz’s late tackle.
Then substitute Nacer Chadli shot an inch wide with the goal gaping.
Conte threw on Willian and Batshuayi but it seemed the ball simply would not drop right for his team.
Rondon’s strength and pace was beginning to be a problem for Chelsea, but Albion had to get men round the Venezualan striker to really punish Chelsea. Fabregas kept prompting, kept probing, but it just was not happening.
