The 21-year-old, who spent last season on loan at Derby, will make his third Champions League appearance on only his ninth senior start for the Blues, having earlier this month been called up by England for the first time.
Tomori is eager to repay the faith shown to him, and Chelsea’s other youngsters, by manager Frank Lampard.
“Coming into the season, I just wanted to stamp my place in the team and the manager gave me an opportunity,” said the defender.
“He’s carried on giving me opportunities. Even if I make mistakes or I’m not quite in the right position, he helps me out and he’s developed me a lot. He talks to me in training, so do the other players, and that helps me.
“This season has been good for me so far. It’s gone better than I probably expected it would go but I’m working hard day in, day out, trying to improve and help the team as much as I can.
“Getting the senior international call-up last month was great and now I just want to keep on going.”
Chelsea have won their last five matches in all competitions, including getting off the mark in Europe at Lille at the start of the month.
But they face a side which, barring a couple of high-profile summer departures, swept into the Champions League semi-finals last season and began this year’s campaign with back-to-back 3-0 victories.
“It will be a very tight one,” added Tomori. “Both teams are in good form and it’s a big game in the group. Ajax is a great club with big history, a great stadium, so we’re expecting a tough game.
“Games like these are where we can learn a lot but every game as a team we’re learning and every game throws up different challenges.
“So far, we’ve handled them well so hopefully we can do the same.”