Newcastle United performed well at the start of the Premier League season, winning against big clubs and scoring plenty of goals against their opponent. Since Newcastle United started playing in the uefa champions league, Newcastle United's performance has reduced and they find it hard to win their matches.
Now Newcastle has been eliminated from the Champions League but their performance has not improved. I don't think Newcastle stage fright in the UCL has had an impact on the EPL, Newcastle performance declined because they were unable to maintain the best game that occurred last season.
The Premier League is very competitive this season, you can see for yourself how the big teams compete in the top four positions. Newcastle needs changes in its team to improve its performance, I doubt Newcastle can repeat last season's success if there is no improvement in performance.