As it turned out, I took CBeisbol's advice and ended up trading for another SP who isn't quite as good as DeWispelaere but is only 24 years old and is one of the best young pitchers in the league.
I have been having too many problems with older veteran players asking for far too many years on contract extensions and being unwilling to accept fewer years, so I decided to see if I could get someone much younger.
I also decided to increase my trade difficulty from normal to hard because I thought I was only getting the DeWispelaere offer because the AI was being too easy on trades. After adding to the difficulty, the AI was still willing to do that deal, even for only my top prospect and not the extra catcher from my reserve list. It was probably because DeWispelaere's contract was expiring and he probably wanted too many years at too much money.
Instead of trading for him, I went for the 24 year-old pitcher but had to give up my top prospect and a solid but 36 year-old starter who was on my reserve list. Now I have four great starters, plus two pitchers in my bullpen who are also starters and have been very good in that #4 spot.
Now I can worry less about having so many 30+ year-old pitchers on my staff, and we have a lot of insurance against injuries in my rotation. But let's hope we never have to use it!
Here are the profiles for my new pitcher and the veteran starter that I had to add to the deal.
Newly Acquired 24 Year-Old Pitcher
Veteran Reserve List SP Traded Away with Top Prospect