As the caption says, that blast means Semien is now tied for the most home runs in a season by a second baseman. He's atop that list with Davey Johnson, who also hit 43 out as the Braves' second baseman in 1973. Prior to this, Semien had been in a three-way tie for second place at 42 with Brian Dozier in 2016 and Rogers Hornsby in 1922.
When we discuss home runs by a player at a certain position, we usually mean those who played at least 75 percent of their games in a given season at that position. In Semien's case, this season has played 140 of his 155 games at second base. Of his 43 home runs, 39 have come as a second baseman. The other four have come as a shortstop, which of course is a more premium position than second base and if anything makes what Semien has achieved even more impressive. In Johnson's case, he hit 42 of his 43 home runs in 1973 as a second baseman and one as a pinch-hitter.
Earlier this season, Salvador Perez of the Royals set the single-season record for home runs by a catcher.
In matters related to all of this, Semien this season is very much in the AL MVP discussion. While Angels two-way threat Shohei Ohtani remains the frontrunner and Semien's teammate Vladimir Guerrero Jr. likely his stiffest competition, Semien merits serious consideration. He's now batting .271/.341/.548 with, as noted, 43 home runs, and he's also stolen 15 stolen bases in 16 attempts. On top of all that, Semien has thrived defensively in his first season as a primary second baseman. Add it all up, and Semien coming into Saturday actually had a higher WAR -- 7.1 to 6.9 -- that Guerrero Jr.
Regardless of how that awards balloting plays out, Semien's 2021 season has been a history-making one. Eligible for free agency this coming winter after signing a one-year pillow contract with Toronto, Semien's also probably headed for a large pay day.