Is blocking SPs unethical/illegal in roto?

[deutschland]

I have enjoyed a comfortable lead down the stretch in my 12 team mixed roto $$$ league . The current 2nd place team is way way behind in games started (limit of 180, ESPN league). I am approaching the starts limit, but not there yet. The 2nd place team has been starting about 7 pitchers per day in order to make up ground in categories like wins and K's and will presumably continue do so for the final week of the season to make a run at me. Noticing this, and having calculated his possible improvement in the standings, I have been picking up certain projected starters for the next day's games in order to prevent him from benefitting from their performances, because I think there is a chance he can catch me and win the league. For the most part, I have not been activating those starters that I have picked up, dropping them the next day and picking up new ones. I do not want to cheat to win my league. ESPN's rules do not appear to touch on this issue. Is this unethical? Is it illegal?