West Brom twice came from behind to equalise, with James McClean's late strike earning the visitors a point in a feisty contest where Diego Costa was one of the main protagonists.
There were six bookings in the game and Claudio Yacob was promptly substituted by West Brom boss Tony Pulis after avoiding a second yellow card for an off-the-ball trip on Costa
Courtois felt the change was telling.
"I think he (Yacob) should have been sent off," Courtois said on chelseafc.com.
"Their manager took the player off one second after the foul so I think everybody knows that was clear.
"We're very disappointed
It was a game we wanted to win
It was a tough game with them playing only long balls, (playing for) second balls, trying to provoke players.
"It was a bit frustrating
We tried to do our best, we came back, but sadly they got the second goal."
Chelsea's frustrations - and Costa's in particular - threatened to boil over at full-time, with the Spain striker angrily hitting the perspex tunnel as he left the field.
Courtois rued the goals conceded, with Pedro losing possession for Craig Gardner's effort and Chelsea twice failing to clear before McClean's leveller.
It left the Blues 14th in the table, 12 points adrift of their target of a top-four place ahead of Saturday's visit of Everton.
"They (the goals) were a bit unlucky," the Belgium goalkeeper added.
"The first, Pedro wanted to come inside and play the ball, but it took a touch to Gardner and he hit a fantastic shot.
"The second came after a free-kick, we tried to head it clear, the ball touched our player and the shot went in the corner again.
"They were unlucky and that's the position we are in at the moment.
"They were goals maybe last year we didn't concede because we were up top, and now they are the kind of goals you concede because you are down there.
"We have to keep on fighting, we have Everton now which will be a difficult game as well, but we have to fight for every game and every point."
Chelsea were suspect in defence, but also less than ruthless up front, with Costa among those spurning chances.
It was put to interim boss Guus Hiddink that Chelsea will at some point claim a handsome win with the chances they create, something which former boss Jose Mourinho also believed.
"We want it to materialise," Hiddink told Chelsea TV.
"That's my concern, a bit, that we create and we are not finishing it totally off."
Baggies boss Pulis praised Gardner for his impact, after coming on as an early replacement for James Morrison.
Scotland midfielder Morrison suffered a hamstring problem, which he had nursed into the game.
"Gardner came in and did really well," Pulis said.
"He filled that pocket well and can strike a ball so well.
"He's one of the best pros I've worked with
He works with the young players, he's here early and always has a great attitude."
Source : PA