Now-retired pitcher Dan Haren was hilariously retrospective on Twitter Monday afternoon, disclosing numerous thoughts and insights from his 13-year career… while working out on a stationary bike.

Among Tweets, former Chicago Cubs teammate Anthony Rizzo managed to slip in a tweet to Haren in his information social media session.

How mad were you when you had to go cover 1st? @ithrow88

-- Anthony Rizzo (@ARizzo44) January 4, 2016

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Haren's response to Rizzo was a priceless diss of his former first baseman.

When your 1st baseman is pushing 300lb's, you gotta bust your ass over. https://t.co/yFvxO2J2lJ

-- dan haren (@ithrow88) January 4, 2016

The fan reactions were priceless as well.

@ithrow88 @ARizzo44 pic.twitter.com/UNbdBZxbrI

-- Allan (@ambp77) January 4, 2016

@ithrow88 @ARizzo44 pic.twitter.com/A38qBYDv0k

-- Mike (@MLermo) January 4, 2016

To be fair, Rizzo is listed at 6' 3", 240 pounds -- shy of the 300 pounds Haren claimed.

Haren was traded to the Cubs from the Miami Marlins at the trade deadline last season. Pitching in 11 games, he had a 4.01 ERA and a 4-2 record for Chicago.