Karstens agreed to a $3.1 million deal to avoid arbitration. He made $1.15 million last year. Meek's contract is worth $875,000 plus $25,000 in performance bonuses.
The Bucs, however, did not reach a deal with Garrett Jones and Casey McGehee ahead of Tuesday's deadline to exchange numbers. The team and the players can continue trying to work out a deal until next month's arbitration hearings.
Karstens, 29, went 9-9 with a 3.38 ERA last year, setting a career high in wins, innings (162 1/3) and strikeouts (96).
If the Pirates and their remaining arbitration-eligible players can't reach a deal, a hearing would be held and either the player's desired salary or the team's offer would be chosen following the hearing. There is no middle ground.
Since Neal Huntington took over as general manager in 2007, the club has mostly avoided extending this process out to an arbitration hearing. The one exception was last year, when Ross Ohlendorf was awarded a $2.025 million salary by winning his hearing.
On Monday, Pittsburgh reached deals with closer Joel Hanrahan and starter Charlie Morton.