Angels monitoring workloads of pitchers Hector Santiago, Andrew Heaney

The Angels don’t plan to put a hard cap on the number of innings Hector Santiago and Andrew Heaney throw this season, but they will monitor both left-handers closely as they surpass their career highs for innings pitched.

Santiago, 27, entered Tuesday night’s start against the Chicago White Sox at U.S. Cellular Field with 129 1/3 innings, and if he were to average six innings over his last nine starts, he would finish the regular season with about 185 innings.

Santiago threw a career-high 149 innings for the Chicago White Sox in 2013 and 141 1/3 innings for the Angels and triple-A Salt Lake in 2014, part of which he spent as a reliever. So Santiago’s workload could increase by as much as 45 innings over last season.

Heaney, 24, has thrown a combined 129 2/3 innings for Salt Lake and the Angels this season, and he is also on pace for about 185 innings, which would be about 22 more than the 166 2/3 innings he threw in the minor leagues and for the Miami Marlins last season.

“You have something in back of your mind,” Manager Mike Scioscia said, when asked if there was a number of innings he was targeting for Santiago and Heaney, “but there’s nothing to say that a guy is not going to be able to jump from 160 to 200 innings.

“We’re watching them. It’s something you always pay attention to, but to say we’re just concerned with it, at this point, we’re not. Hopefully it’s a moot point. We’ll see.”

Before Jerry Dipoto resigned in July as the Angels’ general manager, he said he preferred that pitchers, especially prospects, not jump more than 30 innings from one season to the next.

Heaney is still classified as a “prospect,” especially when compared to the older Santiago, but he has shown little slippage in eight starts since joining the Angels, pitching to a 5-1 record and 2.45 earned-run average.

His worst start was his last one, when he gave up four runs and 10 hits in 5 2/3 innings against the Baltimore Orioles last Friday night.

“With Andrew, you’re always conscious of it,” Scioscia said. “You’re going to be concerned if you start to see him hit a plateau and his stuff diminishes and his command falters. Then you make an evaluation and maybe push him back, freshen him up a bit. He had a rough outing last time, but he’s been pretty good.”