Simplify the following text for a Grade 8 native English-speaking person.
Original: However , the Rockets have advanced past the first round of the playoffs only once since he joined the team , and he has missed significant time due to injury in each of the past six seasons .
Simplified: However , the Rockets have not advanced past the first round of the playoffs since he joined the team , and he has also had injuries in each of the past three seasons .